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CONTEIBUTORS. 


FONES,  ALFRED  C,  D.D.S. 

HOPEWELL-SMITH,  ARTHUR,  Sc.D.,  L.R.C.P.,  M.R.C.S.,  L.D.S. 

KIRK,  EDWARD  C,  D.D.S.,  Sc.D.,  LL.D. 

MERRITT,  ARTHUR  H.,  D.D.S. 

MINER,  LEROY  M.  S.,  M.D.,  D.M.D. 

OTTOLENGUI,  RODRIGUES,  M.D.S.,  D.D.S.,  LL.D. 

STRANG,  ROBERT  H.  W.,  M.D.,  D.D.S. 

THOMA,  KURT  H.,  D.M.D. 

TURNER,  CHARLES  R.,  M.D.,  D.D.S. 


MOUTH  HYGIENE 


A  TEXT-BOOK  FOR  DENTAL  HYGIENISTS 


COMPILED   AND    EDITED    BY 


ALFRED   C.  FONES,  D.D.S. 

BRIDGEPORT,    CONNECTICUT 


SECOND  EDITION,  THOROUGHLY  REVISED 


Timitb  218  lllustrattons  anJ)  8  plates 


LEA   &   FEBIGER 

PHILADELPHIA    AND    NEW    YORK 
1921 


-i(o-  i^^zZ 


Copyright 

LEA   &   FEBIGER 

1921 


PREFACE  TO  THE  SECOND  EDITION. 


Five  years  have  passed  since  the  pubHcation  of  the  first  edition  of 
Mouth  Hygiene,  and  during  that  period  a  number  of  schools  have  been 
organized  for  the  education  and  training  of  the  dental  hygienist. 
The  experience  of  these  schools  has  shown  that  several  of  the  funda- 
mental subjects,  such  as  anatomy,  physiology,  bacteriology,  hygiene 
etc.,  require  more  extensive  text  than  could  be  adequately  covered  in 
any  one  book.  It  is,  therefore,  recommended  that  standard  text-books 
be  utilized  for  such  subjects. 

The  second  edition  of  Mouth  Hygiene  endeavors  to  meet  the  need 
of  the  dental  hygienist  for  those  subjects  which  pertain  directly  to 
dentistry  and  which  are  essential  to  her  education. 

A.  C.  F. 

Bridgeport,  Conn.,  1921. 


LIST  OF  CONTKIBUTOES. 


ALFRED  C.  FONES,  D.D.S., 

Professor  of  Preventive  Dentistry  in  Columbia  University,  New  York  City; 
Director  of  the  Division  of  Dental  Hygiene  in  the  Bridgeport,  Conn., 
Department  of  Health. 

ARTHUR  HOPEWELL-SMITH,  ScD.,   L.R.C.P.,   M.R.C.S.,   L.D.S., 

Professor  of  Dental  Histology,  Histopathology  and  Comparative  Anatomy  in 
the  LTniversity  of  Pennsylvania,  Philadelphia. 

EDWARD  C.  KIRK,  D.D.S.,  Sc.D.,  LL.D., 

Editor  of  the  Dental  Cosmos. 

ARTHUR  H.  MERRITT,  D.D.S., 

Specialist  in  Periodontia,  New  York  City. 

LEROY  M.  S.  MINER,  M.D.,  D.M.D., 

Associate  Professor  of  Dentology  in  the  Boston  University  School  of  Medicine; 
Assistant  Professor  of  Oral  Surgery  in  the  Dental  School  of  Harvard  Uni- 
versity, Boston,  Mass.;  Consulting  Oral  Surgeon  to  the  Children's  Hospital; 
Oral  Surgeon  in  the  Forsyth  Infirmary  for  Children;  Chief  of  the  Dental 
Service  in  the  Massachusetts  General  Hospital,  Boston,  Mass. 

RODRIGUES  OTTOLENGUI,  M.D.S.,  D.D.S.,  LL.D., 

Editor  of  Dental  Items  of  Interest. 

ROBERT  H.  W.  STRANG,  M.D.,  D.D.S., 

Specialist  in  Orthodontia;  Oral  Surgeon  to  the  Bridgeport  Hospital,  Bridgeport, 
Conn. 

KURT  H.  THOMA,  D.M.D., 

Assistant  Professor  of  Oral  Anatomy  and  Pathology  in  the  Harvard  University 
Dental  School,  Boston,  Mass. 

CHARLES  R.  TURNER,  M.D.,  D.D.S., 

Dean  of  the  School  of  Dentistry  in  University  of  Pennsylvania,  Philadelphia. 


CONTENTS. 


CHAPTER  I. 

ANATOMY  OF  THE  HEAD 17 

By  Robert  H.  W.  Strang,  M.D.,  D.D.S. 

CHAPTER  II. 

HISTOLOGY  OF  THE  TEETH  AND  ASSOCIATED  STRUCTURES  .       58 
By  Robert  H.  W.  Strang,  IM.D.,  D.D.S. 

CHAPTER  III. 

THE  TEETH  AS  A  MASTICATING  MACHINE 80 

By  Charles  R.  Turner,  M.D.,  D.D.S. 

CHAPTER  IV. 

MALOCCLUSION  OF  THE  TEETH 112 

By  Rodrigtjes  Ottolengtji,  M.D.S.,  D.D.S.,  LL.D. 

CHAPTER  V. 

INFLAMMATION 136 

By  Leroy  M.  S.  Miner,  M.D.,  D.M.D. 

CHAPTER  VI. 

DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 149 

By  Edward  C.  Kirk,  D.D.S.,  Sc.D.,  LL.D. 

CHAPTER  VII. 

PYORRHEA  ALVEOLARIS 166 

By  Arthur  H.  Merritt,  D.D.S. 

CHAPTER  VIII. 

DENTAL  CARIES 173 

By  Edward  C.  Kirk,  D.D.S.,  Sc.D.,  LL.D.       . 


viii  CONTENTS 


CHAPTER  IX. 

ODONTALGIA  AND  NEURALGIA 191 

By  Arthur  Hopewell-Smith,  Sc.D.,  L.R.C.P.,  M.R.C.S.,  L.D.S. 

CHAPTER  X. 

THE  RELATION  OF  ORAL  INFECTIONS  TO  GENERAL  HEALTH    .     203 
By  Kurt  H.  Thoma,  D.M.D. 

CHAPTER  XI. 

DENTAL  PROPHYLAXIS 223 

By  Alfred  C.  Fones,  D.D.S. 

APPENDIX 299 


MOUTH  HYGIENE. 


CHAPTER  I. 

ANATOMY  OF  THE  HEAD.i 

By  ROBERT  H.  W.  STRANG,  M.D.,  D.D.S. 

THE  SKULL. 

The  twenty-two  bones  that  enter  into  the  formation  of  the  osseous 
framework  of  the  head  are  united  by  immovable  joints,  the  lower 
jaw  excepted,  called  sutures.  These  form  a  strong  supporting  and 
protecting  structure  termed  the  skull  (Fig.  1).  This  may  be  con- 
veniently studied  under  four  headings:  (a)  the  cranium;  (6)  the  base; 
(c)  the  lateral  aspect;  (d)  the  anterior  aspect  or  face. 

The  Cranium. — The  cranium  comprises  that  portion  of  the  skull 
which  contains  the  brain.  It  is  formed  by  the  union  of  eight  bones 
which  are  named  as  follows:  frontal,  two  parietal,  occipital,  two  tem- 
poral, sphenoid  and  ethmoid.  In  outline  it  is  somewhat  egg-shaped 
and  presents  for  study  a  superior  surface,  forming  the  vertex  of  the 
skull,  and  an  inferior  surface. 

The  external  surface  of  the  vertex  is  convex  and  is  covered  in  the 
living  subject  by  the  tissues  that  form  the  scalp.  This  convexity  of 
surface  is  ideal  for  the  resisting  and  warding  off  of  blows.  This  surface 
is  traversed  by  three  sutures  arranged  in  the  form  of  the  letter  "H." 
The  anterior  cross  suture  which  is  situated  well  toward  the  top  of  the 
skull  is  called  the  coronal;  the  one  passing  from  this  to  the  posterior 
cross  suture  is  the  sagittal;  the  posterior  transverse  suture  is  the 
lambdoid. 

The  internal  surface  of  the  vertex  is  concave  and  is  marked  with 
elevations  and  depressions  for  the  accommodation  of  the  irregular 
brain  surface.  Through  the  center,  running  anteroposteriorly,  is  a 
groove  in  which  lies  the  superior  longitudinal  sinus,  a  blood  channel 
performing  the  function  of  a  vein  and  carrying  part  of  the  return 
blood  from  the  brain.  To  the  margins  of  this  groove  are  attached 
some  of  the  supporting  membranes  of  the  brain. 

1  Bibliography:    Gray's  Anatomy;  Piersol's  Anatomy;  Cryer,  Internal  Anatomy  of 
the  Face;  Deaver,  Special  Anatomy  of  Head  and  Neck;  Swan,  Manual  of  Anatomy; 
Chapter  on  Anatomy  of  the  Teeth,  by  C.  R.  Turner,  in  Johnson's  Operative  Dentistry. 
2 


18 


ANATOMY  OF  THE  HEAD 


There  are  also  numerous  smaller  grooves  in  the  bony  surface  which 
radiate  in  various  directions  and  in  appearance  resemble  the  branches 
of  a  tree.  In  these  run  the  ramifying  branches  of  the  middle  meningeal 
artery  which  supplies  the  cranial  bones  and  dura  mater  with  blood. 

The  inferior  surface  of  the  cranium  corresponds  to  the  cerebral 
surface  of  the  base  of  the  skull  (Fig.  2) .  It  is  divided  by  two  trans- 
verse ridges  into  three  planes,  arranged  like  terraces  with  the  anterior 
one  on  the  highest  level.  These  planes  bear  the  name  of  fossce  and 
are  called  according  to  their  position,  anterior,  middle  and  posterior. 
Their  surfaces  are  more  or  less  irregularly  concave,  grooved  to  accom- 
modate bloodvessels  and  perforated  in  many  places  to  allow  these 
vessels  and  also  nerves  to  pass  in  and  out  of  the  cranium. 


ANTERIOR    NA 
SPINE 


GNATHIONi 


Fig.  1. — Side  view  of  typical  skull.     According  to  the  present  nomenclature  the  bone 
marked  malar  should  be  zygoma  and  that  zygoma  should  be  zygomatic  arch.   (Cryer.) 


Description  of  the  Fossae. — Anterior  Fossa. — The  points  of  interest 
in  this  fossa  are  (a)  the  prominent  bony  spine  in  the  median  line 
called  the  crista  galli  (cock's  crest);  (6)  near  the  front  end  of  this 
on  either  side,  slit-like  openings  for  the  passage  of  the  nasal  nerves 
into  the  nasal  cavity;  (c)  the  cribriform  plate  of  the  ethmoid  bone 
placed  on  a  somewhat  lower  level  than  the  rest  of  the  floor  of  the 
anterior  fossa  forming  what  is  known  as  the  olfactory  groove.  This 
groove  is  divided  anteroposteriorly  by  the  crista  galli,  accommodates 
the  olfactory  bulb  of  the  brain  and  has  its  floor  pierced  with  many 


THE  .SKULL  19 

openings  for  the  passage  of  the  olfactory  nerves  to  the  nasal  cavities; 
(d)  the  anterior  and  posterior  ethmoidal  foramina,  situated  at  the 
outer  edge  of  the  cribriform  plate,  the  former  at  about  the  middle 
and  the  latter  at  the  posterior  end  of  the  plate.  The  bone  forming 
the  floor  of  the  anterior  fossa  roofs  over  the  orbital  cavities. 

Middle  Fossa. — In  the  middle  fossa  are  seen  (a)  two  openings  that 
communicate  with  the  orbits.  The  smaller  of  these  is  the  ojJtic  fora- 
men, transmitting  the  optic  nerve  and  ophthalmic  artery  to  the  eye; 
the  larger  one  is  the  siihenoidal  fissure  or  anterior  lacerated  foramen, 
for  the  passage  of  the  third,  fourth,  ophthalmic  division  of  the  fifth 
and  the  sixth  cranial  nerves,  a  s^inpathetic  nerve,  and  also  arteries 
and  veins  to  and  from  the  orbits;  (/>)  in  the  center  of  the  fossa  a  bony 
formation  that  resembles  a  saddle  and  for  this  reason  is  called  the  sella 
turcica  (Turkish  saddle) .  In  this  bony  structure  is  situated  the  pitui- 
tary body,  one  of  the  so-called  ductless  glands,  which  secretes  important 
hormones  that  exert  a  marked  influence  on  growth  and  development; 
(c)  on  either  side  of  this,  four  openings.  The  two  anterior  ones  are 
of  particular  interest  because  through  them  pass  the  divisions  of  the 
fifth  cranial  nerve  that  go  to  the  upper  and  lower  teeth.  The  anterior 
opening  is  the  foramen  rotundum  and  it  transmits  the  superior  maxillary 
division  of  the  fifth  nerve.  Behind  this  is  the  foramen  ovale  through 
which  passes  the  sensory  and  motor  portions  of  the  inferior  maxillary 
division  of  the  same  nerve.  The  smallest  of  the  openings  is  the 
foramen  spinosum  through  which  the  middle  meningeal  artery  enters 
the  skull.  The  largest  of  these  four  foramina  is  called  the  middle 
lacerated  foramen.  This  is  closed  in  the  living  subject  with  cartilage. 
On  its  posterior  wall,  however,  is  seen  (rf)  the  inner  opening  of  the 
carotid  canal  through  which  the  internal  carotid  artery  gains  entrance 
to  the  cranium. 

The  bone  at  the  posterior  aspect  of  the  middle  fossa  acts  as  the 
roof  for  the  middle  and  internal  divisions  of  the  ear  and  is  somewhat 
irregular  in  conformation  with  their  make-up. 

Posterior  Fossa. — The  surface  of  this  fossa  is  deeply  concave  and 
accommodates  the  cerebellum.  It  is  marked  with  (a)  grooves  for  the 
lateral  sinuses  carrying  return  blood  from  the  brain.  To  the  edges 
of  these  grooves  is  attached  the  membrane  supporting  the  cerebellum. 
(6)  The  foramen  magnum,  centrally  located,  through  which  passes  the 
spinal  cord;  (c)  the  anterior  condyloid  foramina  for  the  passage  of 
the  h}T)oglossal  nerves  to  the  tongue;  {d)  the  jugular  or  posterior 
lacerated  foramina  which  affords  a  means  of  exit  to  the  ninth,  tenth 
and  eleventh  cranial  nerves  as  well  as  the  lateral  sinuses;  ie)  the 
internal  auditory  meati  for  the  passage  of  the  auditory  nerves  and 
arteries  and  the  facial  nerves. 

The  Base  of  the  Skull. — The  cerebral  surface  of  the  base  has  just  been 
described  under  the  heading  of  the  Inferior  Surface  of  the  Cranium 
(Fig.  2). 


20 


ANATOMY  OF  THE  HEAD 


Groove  for  super,  sagittal  sinus 

Grooves  for  anter.  meningeal  vessels 

Foramen  ccecum 

Crista  galli 

Slit  for  nasociliary  nerve 

Groove  for  nasociliary  nerve 

Anterior  ethmoidal  foramen 

Orifices  for  olfactory  nerves 
Posterior  ethmoidal  foramen 

Ethmoidal  spine 


Olfactory  grooves 

Optic  foramen 

Chiasmatic  groove 

Tuberculum  sellae 

Anterior  clinoid  process 

Middle  clinoid  process 

Posterior  clinoid  process 

Groove  for  abducent  nerve 

Foramen  lacerum 

Orifice  of  carotid  canal 

Depression  for  semilunar  ganglion 


Internal  acoustic  meatus 

Slit  for  dura  mater 

Groove  for  superior  petrosal  sinus 

Jugular  foramen 

Hypoglossal  canal 

Aquceduetus  ve^tibuli 

Condyloid  foramen 


Mastoid  foramen 
Posterior  meningeal  grooves 


Fig.  2. — Base  of  the  skull.     Inner  or  cerebral  surface.     (Gray.) 


THE  SKULL 
Incisors 


21 


Canine 


Incisive,  canal 


Transmits  left  nasopalatine  nerve 
Traiunaits  desceiuiiiuj  palatine  vesseh 
Transmits  right  nasopalatine  nerve 


Lesser  palatine  foramina 

Posterior  nasal  spine 
Musculus  uvvlae 
Pterygoid  hamulus 


Sphenoidal  process  of  palatine 
-Pharyngeal  carml 


Pharyngeal  tubercle 
Bituaiion   of  auditory   tube  and 
semicanal  for  Tensor  tympani 
Tensor  veli  palatini 
Inferior  tympanic  canaliculus 
Aqtiaednctus  rorfJeae 
Jugular  foraimn 
Mastoid  canaliculus 
Tympanomastoid  fissure 


Fig.  3.— Base  of  tlio  skull.     External  surface.     (Oray.) 


22  AX  ATOMY  OF   THE  HEAD 

The  external  or  inferior  surface  of  the  base  (Fig.  3)  (the  mandible 
removedj  presents  the  following  points  for  study:  (a)  In  front  is  the 
hard  palate  bordered  by  the  teeth.  Behind  the  incisor  teeth  is  a  depres- 
sion in  the  palate  known  as  the  anterior  imlatine  fossa.  In  the  floor 
of  this  fossa  are  four  foramina  for  the  passage  of  the  naso-palatine 
nerves  and  bloodvessels  from  the  nose.  On  the  hard  palate  opposite 
the  last  molar  teeth  are  the  posterior  -palatine  foramina  transmitting 
the  descending  palatine  arteries  and  the  anterior  palatine  ners'es  to  the 
hard  palate.  (6)  Behind  the  hard  palate  are  seen  the  posterior  openings 
of  the  nasal  cavities  on  the  outer  sides  of  which  are  the  two  pterygoid 
processes  of  the  sphenoid  bone,  (c)  External  to  these  processes  are 
the  zygomatic  fossce  which  contain  three  of  the  large  muscles  of  mastica- 
tion, the  inferior  maxillary  division  of  the  fifth  nerve  and  the  internal 
maxillary  artery.  These  fossae  communicate  with  the  orbits  by  means 
of  the  large  sphenomaxillary  fissures,  (d)  Numerous  foramina  the  most 
important  of  which  are:  ovale,  external  opening  of  the  carotid  canal, 
stylo-mastoid,  posterior  lacerated,  condyloid  and  magnum,  (e)  Two 
pairs  of  articulating  surfaces,  the  one  to  receive  the  condyles  of  the 
mandible  and  named  the  glenoid  fossce,  the  other  to  articulate  with  the 
first  vertebra,  (f)  The  styloid  and  mastoid  processes  which  form  pro- 
nounced landmarks  and  serve  for  the  attachment  of  muscles. 

The  Lateral  Aspect  of  the  Skull  fFig.  1). — The  following  landmarks 
present  themselves  for  study,  (a)  The  malar  bone  that  forms  the  prom- 
inence of  the  cheek,  (b)  The  zygoma  which  lies  very  superficially  and 
affords  attachment  to  the  masseter  muscle,  (c)  The  external  auditory 
meatus  and  (d)  the  styloid  and  mastoid  processes.  It  is  of  interest 
to  note  that  practically  all  of  the  bone  that  enters  into  the  formation 
of  the  side  of  the  skull  above  the  zygoma  is  covered  by  the  largest  of 
the  muscles  of  mastication,  i.  e.,  the  temporal. 

The  Anterior  Aspect  of  the  Skull  or  Face. — The  anterior  portion  of 
the  skull  is  termed  the  face.  The  follo'^dng  fourteen  bones  enter  into 
its  make-up:  two  nasal,  two  lachrymal,  the  vomer,  two  superior 
maxillary,  two  malar,  two  inferior  turbinates,  two  palate  and  the 
mandible.  Passing  from  above  downward  the  following  points  of 
interest  are  noted :  (a)  The  supra-orbital  foramina  or  notches  through 
which  pass  arteries  and  nerves  bearing  the  same  names,  (b)  The  orbits, 
in  which  well-protected  cavities  lie  the  eyes,  (c)  The  nasal  fossae. 
(d)  The  infra-orbital  foramina  which  transmit  the  infra-orbital  arteries 
and  the  end-branches  of  the  superior  maxillary  nerves,  (e)  The 
prominent  malar  bones,  (f)  The  teeth  of  the  upper  and  lower  jaws 
supported  by  their  alveolar  processes,  (g)  The  mental  foramina 
through  each  of  which  an  artery  and  nerve  of  the  same  name  emerge. 
(h)  The  mandible  or  lower  jaw. 

The  Orbits. — These  are  irregular,  conical  cavities,  with  the  base 
toward  the  exterior  and  the  apex  inward.  The  outer  edge  of  the 
base  is  in  the  form  of  a  strong  bony  ridge  which  projects  a  little  beyond 
the  e^'e  and  thus  protects  it  from  injury.     Seven  bones  enter  into  the 


THE  SKULL  23 

formation  of*  the  walls  of  the  orl)its.  On  the  superior  aspect  of  the 
outer  wall  near  the  base  is  a  depression  for  the  lachrymal  gland.  Each 
orbit  is  in  communication  with  various  other  cavities  and  fossse  by 
means  of  the  following  openings:  (a)  The  optic  foramen  and  (6) 
sphenoidal  fissure  open  into  the  middle  fossa  of  the  cranial  cavity;  (c) 
the  sphenomaxillary  fissure  gives  entrance  into  the  sphenomaxillary 
and  zygomatic  fosstt;  (d)  on  the  inner  wall,  the  anterior  and  posterior 
ethmoidal  foramina,  which  transmit  vessels  of  the  same  names  and  the 
former  also  the  nasal  nerve,  lead  into  the  anterior  fossa;  and  (e)  the 
nasal  duct  opens  into  the  nose.  The  posterior  opening  of  the  infra- 
orbital canal  is  seen  on  the  floor  of  the  orbital  cavity. 


i 

J],-Ostium 
rnaxillare 


First  molar  First  molar 

Fig.  4. — Vertical  transverse  section  of  typical  skull.     (Cryer.) 

The  Nasal  Fossae  (Fig.  4). — These  are  large,  irregular  shaped  cavities 
extending  from  the  floor  of  the  cranium  to  the  roof  of  the  mouth.  They 
are  separated  from  each  other  by  a  thin  partition  made  up  of  bones 
.and  cartilage  and  called  the  nasal  septum. 

In  front  these  fossae  communicate  with  the  exterior  by  means  of 
two  large  openings  called  the  anterior  nares.  In  back  they  open  into 
the  pharynx  through  the  posterior  nares  or  choancB. 

The  lateral  walls  are  very  irregular  and  are  divided  by  shelf-like 
bones  named  turbinates  (scroll-like)  into  three  or  more  sections  called 
meati.  The  turbinate  bones  are  normally  three  in  number  and  accord- 
ing to  their  position  receive  the  names  of  inferior,  .niddle  and  superior. 

The  floor  of  the  nose  is  formed  by  the  same  bones  that  make  up 
the  hard  palate,  i.  e.,  the  palatal  processes  of  the  superior  maxillary 


24  ANATOMY  OF  THE  HEAD 

and  the  horizontal  processes  of  the  palate  bones.  The  superior  surface 
of  these  processes  receives  the  name,  "floor  of  the  nose,"  while  the 
inferior  surface  is  called  the  "roof  of  the  mouth." 

The  nasal  fossse  are  in  communication  by  means  of  openings  and 
canals  with  the  following  cavities:  (a)  The  cranium,  (6)  the  orbits, 
(c)  the  pharynx,  (d)  the  mouth,  (e)  three  sinuses,  i.  e.,  maxillary,  frontal 
and  sphenoidal,  and  (/)  three  sets  of  air  cells,  i.  e.,  anterior,  middle 
and  posterior  ethmoidal. 

According  to  function  the  nasal  fossge  are  divided  into  two  parts, 
the  olfactory  and  respiratory.  The  olfactory  area  is  in  the  upper 
portion  and  extends  down  to  include  the  middle  turbinate  bones 
on  the  one  side  and  two-thirds  of  the  septum  on  the  other.  The 
respiratory  portion  takes  in  the  remainder  of  the  cavity. 

The  nose  is  lined  with  mucous  membrane  which  in  the  olfactory 
portion  is  non-ciliated  but  contains  cells  that  are  speciaHzed  to  receive 
the  sensations  productive  of  smell.  That  in  the  respiratory  portion 
is  much  thicker,  contains  large  plexuses  of  veins  and  its  cells  are  of 
the  ciliated  variety.  Many  glands  are.  found  in  the  mucous  membrane 
of  both  portions  of  the  nasal  cavities.  Their  secretion  is  poured  upon 
the  free  surface  of  the  membrane  keeping  this  moist.  The  inspired 
air  is  warmed  as  it  passes  over  this  membrane  due  to  the  heat  imparted 
from  the  great  amount  of  blood  found  in  the  large  venous  plexuses. 

The  hlood  supply  to  the  nasal  cavity  comes  through  the  internal 
maxillary,  the  ophthalmic  and  the  facial  arteries. 

The  nerve  supply  is  of  two  kinds:  (a)  that  of  special  sense  through 
the  first  cranial  or  olfactory  nerve  and  (6)  that  of  common  sensation 
through  the  fifth  cranial  or  trifacial  nerve. 

The  Bony  Sinuses  and  Air  Cells.— In  all  of  the  bones  of  the  skull 
that  have  any  great  bulk  we  find  cavities.  The  largest  of  these  cavities 
are  called  sinuses  while  the  smaller  ones  are  called  air  cells.  Their 
function  is  to  reduce  the  weight  of  the  bone  and  in  the  region  of  the 
mouth  and  nose  to  render  the  bone  more  resonant  for  the  purpose  of 
speech.  The  most  important  of  these  sinuses  and  air  cells  are  the 
following : 

Maxillary  or  Antra  of  Highmore. 

Sphenoidal. 

Frontal. 

Anterior,  Middle  and  Posterior  Ethmoidal. 

Mastoid. 

The  Maxillary  Sinuses  or  Antra  of  Highmore  (Fig.  4). — ^These  are  two 
in  number,  situated  within  the  bodies  of  the  superior  maxillary  bones, 
external  to  the  nose  and  below  the  orbits.  In  shape  they  are  some- 
what pyramidal,  with  their  bases  directed  toward  the  nose  and  the 
apices  at  the  prominence  of  the  cheek.  They  open  into  the  middle 
meati  of  the  nose  at  points  known  as  the  infundibula.  The  antra  are 
often  divided  and  partitioned  by  bony  septa.  They  are  lined  with 
mucous  membrane  which  is  directly  continuous  with  that  of  the  nose 


THE  SKULL 


25 


and  is  covered  with  ciliated  epithelium.  The  mucous  membrane  also 
contains  glands.  Often  the  roots  of  the  molar  and  biscuspid  teeth 
form  elevations  on  the  floors  of  the  sinuses  and  when  diseased  frequently 
infect  the  mucous  membrane  with  most  serious  results. 

The  Sphenoidal  Sinus  (Fig.  5). — This  air  cavity  may  be  a  single  one 
but  is  usually  partitioned  into  two  distinct  cells.    It  is  situated  within 


Section  turned  • 


Sella  turcica 


Auditory  orifice 


Posterior  ethmoidal  cells 


Right  frontal 
sinus 


Left  frontal 
sinus 


Infundibulum 

Anterior 

ethmoidal  cells 
Hiatus 

semilunaris 
Unciform 

process 

Middle  meatus 


Inferior  concha 
Probe  passing 

into  lacrimal 

duct 
Inferior  meatus 


Hard  palate 


Alveolar 
process 


Fig.  5. 


-An  anteroposterior  section  within  the  nasal  cavity,  with  the  middle  concha 
and  portion  of  the  cell  walls  turned  up.     (Cryer.) 


the  body  of  the  sphenoid  bone  at  the  posterior  aspect  of  the  roof  of  the 
nose.  It  has  an  opening  into  the  superior  meatus  and  is  also  lined  with 
mucous  membrane  continuous  with  that  of  the  nasal  cavity.  Often 
the  posterior  ethmoidal  air  cells  communicate  with  this  sinus. 

The  Frontal  Sinuses  (Fig.  5). — These  are  two  fairly  large  cavities 
within  the  frontal  bone.  They  are  located  immediately  above  the 
orbits  and  their  position  is  marked  approximately  by  the  eyebrows. 


26  ANATOMY  OF  THE  HEAD 

They  are  really  a  continuation  of  the  anterior  ethmoidal  air  cells  of 
their  respective  sides.  They  open  into  the  middle  meati  of  the  nose. 
Congestion  of  these  sinuses  is  a  usual  sequence  in  a  so-called  "  cold  in 
the  head,"  and  gives  rise  to  the  accompanying  headache  so  frequently 
noted  in  this  condition. 

The  Ethmoidal  Air  Cells  (Fig.  5). — There  are  three  sets  of  these  found 
within  the  lateral  masses  of  the  ethmoid  bone  and  named  according  to 
their  position,  anterior,  middle  and  posterior.  They  are  lined  with 
mucous  membrane  which  is  a  continuation  of  that  lining  the  nasal 
passages  into  which  each  set  of  cells  opens.  These  cells  are  often  inter- 
connected and  frequently  the  posterior  set  communicates  with  the 
sphenoidal  sinus.  ^ 

The  orifices  of  the  canals  that  lead  from  the  nose  to  the  anterior 
ethmoidal  cells  are  intimately  associated  with  the  openings  into  the 
antra  and  into  the  frontal  sinuses.  Thus  it  is  that  the  antrum,  the 
anterior  ethmoidal  cells  and  the  frontal  sinus  of  each  side  are  made 
intercommunicating  and  their  mucous  membrane  linings  practically 
continuous  with  each  other.  These  anatomical  facts  make  it  very 
possible  for  an  infection  arising  within  one  cavity  to  travel  to  one  or 
both  of  the  others.  Cases  are  not  uncommon  in  which  an  abscess  on 
the  root  of  an  upper  molar  or  bicuspid  tooth  infects  the  mucous  mem- 
brane of  the  antrum  and  the  discharge  from  this  tissue  passing  into  the 
nose  infects  the  lining  membrane  of  the  canal  that  leads  to  the  anterior 
ethmoidal  air  cells.  The  infection  traveling  up  this  canal  will  event- 
ually involve  these  cells.  The  mucous  membrane  of  the  frontal  sinus 
may  also  become  involved  from  the  same  source,  either  by  an  extension 
from  the  nasal  mucous  membrane  or  directly  from  that  of  the  anterior 
ethmoidal  cells.  Such  a  pathological  condition  may  be  continued  into 
the  middle  and  posterior  ethmoidal  cells  and  the  sphenoidal  sinus. 

The  mastoid  air  cells  or  antra  are  situated  within  the  mastoid  portion 
of  the  temporal  bones  and  will  be  mentioned  under  the  description  of 
the  ear. 

THE  EYES. 

These  are  the  organs  of  vision  and  consist  of  two  globular  bodies 
situated  within  the  orbits.  They  are  freely  movable  by  means  of  a 
ball-and-socket  joint  formed  between  the  eyeball  and  a  tough,  fibrous 
membrane  arranged  in  the  form  of  a  socket.  This  membrane  receives 
the  name  of  the  ca'psule  of  Tenon.  Movement  of  the  eyeball  is  per- 
formed through  the  agency  of  six  muscles  that  arise  from  the  bony 
wall  of  the  orbit  and  are  attached  to  the  ball  at  various  points. 

The  anterior  portion  of  the  eye  is  covered  with  a  modified  mucous 
membrane  which  is  reflected  on  to  the  lids  and  lines  the  inner  side 
of  these.  This  membrane  is  called  the  conjunctiva  and  covers  that 
portion  of  the  eye  that  is  commonly  called  the  "white." 

The  eyeball  (Fig.  6)  is  made  up  of  three  coats  within  which  are 
three  refracting  media.     The  coats  are  named: 


THE  EYES 


27 


1.  Outer  or  fibrous. 

2.  Middle  or  vascular. 

3.  Inner  or  nervous. 
The  refracting  media  are: 

1.  Aqueous  humor. 

2.  Crystalline  lens. 

3.  Vitreous  humor. 


Sulcus  circularvi  cornecB 
Posterior  chamber 

Conjunctiva 


Sulcus  drcularis  comece 
Ciliary  body 


Rectus 
lateralis 


Zonular  spaces 


Hyaloid  canal 

Rectus 
medialis 


Sclera 

Choroid 

Retina 


A.  centralis  retinae 

y\\'\\\\\\\\h2>^  Optic  nerve 

Fovea  centralis  /u.wwwu-as 

Nerve  sheath 
Fig.  6. — The  right  eye  in  horizontal  section.     (Toldt.) 

The  Coats  of  the  Eye. — Fibrous  Coat. — This  is  divided  into  two 
parts:  (a)  Cornea,  forming  the  anterior  sixth  of  the  sphere  and  (&) 
the  sclera,  forming  the  remainder,  (a)  The  Cornea.  This  tissue  is 
made  up  of  cells  that  will  transmit  the  rays  of  light  and  so  may  be 
likened  to  a  window.  It  is  more  highly  convex  than  the  rest  of  the 
eyeball,  giving  this  portion  of  the  ball  a  bulging  appearance.  Its 
posterior  edge  is  continued  into  the  sclera.  (6)  The  Sclera.  This  is 
a  firm,  inelastic,  fibrous  membrane  forming  the  posterior  five-sixths 
of  the  eyeball. 

Vascular  Coat. — This  is  divided  into  three  parts: 

The  iris. 

The  ciliary  body. 

The  choroid. 


28  ANATOMY  OF  THE  HEAD 

(a)  The  iris  may  be  likened  unto  a  circular  curtain  attached  at  the 
periphery  and  perforated  in  the  center.  This  "hole"  in  the  center 
is  called  the  pupil.  The  iris  contains  pigment  of  varying  tint  and  is 
the  tissue  that  gives  the  color  to  the  eye.  In  structure  it  consists 
for  the  most  part  of  muscular  fibers  of  two  kinds,  circular  and  radi- 
ating. When  the  circular  contract  the  pupil  becomes  smaller  and 
when  the  radiating  are  active  the  pupil  enlarges. 

The  iris  is  suspended  in  a  cavity  formed  by  the  cornea  in  front  and 
the  lens  behind.  It  is  nearly  in  contact  with  the  latter  structure. 
This  cavity  is  filled  with  a  modified  lymph  called  the  aqueous  humor. 

(6)  The  ciliary  body  is  made  up  of  the  ciliary  processes  and  the 
ciliary  muscle.  The  ciliary  processes  are  composed  of  foldings,  as  it 
were,  of  the  tissues  making  up  the  middle  coat  and  are  continuous  at 
their  posterior  ends  with  the  choroid  and  at  their  anterior  ends  with 
the  suspensory  ligament  of  the  lens  and  the  iris.  They  vary  from  sixty 
to  eighty  in  number.  The  ciliary  muscle  is  arranged  in  the  form  of  a 
circular  band  of  involuntary  muscle  fibers  lying  on  the  outer  surface 
of  the  middle  coat  of  the  eye  between  the  iris  and  the  choroid.  Its 
function  is  to  control  the  convexity  of  the  lens  so  that  the  rays  of  light 
may  be  properly  focused.  The  ciliary  body  is  an  exceedingly  vascular 
area  and  consequently  is  very  liable  to  be  the  seat  of  an  infection, 
hence  it  has  been  designated  as  the  "danger  area"  of  the  eye. 

(c)  The  choroid  is  that  portion  of  the  middle  coat  that  lies  posterior 
to  the  ciliary  body.  It  is  made  up  of  areolar  tissue,  bloodvessels, 
and  considerable  pigment. 

Nervous  Coat. — This  is  commonly  called  the  retina.  It  is  continuous 
with  the  optic  nerve  behind  and  extends  forward  about  as  far  as  the 
ciliary  body  where  it  ends  in  a  jagged  margin.  It  may  be  called  the 
end-organ  of  the  optic  nerve  with  the  special  sense  of  vision  as  its 
function. 

The  fibers  of  the  optic  nerve  are  distributed  to  all  parts  of  this 
membrane  and  end  in  physiological  relationship  with  special  cells, 
the  rods  and  cones,  of  the  neuro-epithelium  lining  the  retina.  The 
rods  and  cones  receive  the  visual  impressions  and  transfer  them  to 
the  nerve  fibers. 

In  examining  the  retina  a  white  circular  area  is  noted  at  the  point 
of  entrance  of  the  optic  nerve.  This  is  called  the  optic  disc  and  is  the 
one  point  on  the  membrane  where  the  rays  of  light  will  make  no 
impression.  In  other  words,  it  is  a  blind  spot.  For  this  reason  it  is 
located  eccentrically  so  that  the  same  rays  of  light  will  not  be  received 
on  a  blind  spot  in  each  eye,  damaging  the  field  of  vision.  Its  position 
is  somewhat  to  the  inner  side  of  the  center.  Directly  in  the  center  of 
the  retina  is  the  area  where  the  most  acute  vision  is  to  be  had.  This 
is  called  the  macula  lutea  (yellow  spot)  because  of  its  color.  In  the 
center  of  this  is  a  depression  known  as  \h.e  fovea  centralis. 

The  Interior  of  the  Eyeball. — ^The  interior  of  the  eyeball  is  unequally 
divided  by  the  lens.    That  portion  in  front  of  the  lens  is  further  sub- 


THE  EARS  29 

divided  by  the  iris  into  two  compartments  known  as  the  anterior  and 
posterior  chambers.  The  anterior  chamber  communicates  with  the 
posterior  chamber  through  the  pupih 

The  Refracting  Media. — The  Aqueous  Humor.— This  is  a  watery  fluid 
fining  the  anterior  and  posterior  chambers  of  the  eye.  It  is  derived 
from  the  vessels  within  the  ciHary  body  and  any  excess  is  carried  off 
through  spaces  and  canals  that  empty  into  the  ciliary  veins. 

The  Crystalhne  Lens. — This  is  a  biconvex,  circular  body  made  up  of 
transparent  fibrous  tissue  the  component  parts  of  which  are  cemented 
together  with  a  transparent  cement  substance  and  the  entire  mass  of 
tissue  is  surrounded  by  a  capsule.  It  lies  in  a  depression  on  the 
anterior  surface  of  the  vitreous  body  and  is  held  in  position  by  the 
susyensory  ligament  of  the  lens.  The  function  of  the  lens  is  to  bring 
the  rays  of  light  to  a  proper  focus  upon  the  retina. 

The  Vitreous  Humor  or  Body. — In  contact  with  the  retina  and  filling 
the  interior  of  the  eyeball  behind  the  lens  is  the  vitreous  humor.  It 
is  composed  of  a  soft,  jelly-like  substance,  perfectly  transparent,  and 
made  up  of  semisolid  connective  tissue.  This  is  surrounded  by  a 
membrane  that  is  thickened  anteriorly  to  form  the  suspensory 
ligament  of  the  lens  which  holds  the  lens  in  position  and  affords  attach- 
ment to  the  ciliary  processes.  The  anterior  surface  of  the  vitreous 
body  presents  a  cup-like  depression  into  which  the  lens  fits. 

The  Lachrymal  Apparatus. — This  consists  of  (a)  the  lachrymal  or 
tear  gland  which  is  situated  in  a  depression  at  the  outer  angle  of  the 
orbit  at  its  upper  aspect  and  from  which  several  ducts  lead  and  open 
through  the  conjunctiva  of  the. upper  lid  just  before  this  is  reflected 
on  to  the  eyeball;  (b)  the  lachrymal  sac,  placed  at  the  inner  angle  of 
the  orbit  and  gathering  in  the  tears  by  means  of  two  small  canals 
leading  from  the  inner  corner  of  each  lid;  and  (c)  the  nasal  duct,  a 
passage  that  leads  from  the  sac  to  the  inferior  meatus  of  the  nose 
and  discharges  its  contents  into  this  cavity. 

THE  EARS. 

The  organ  of  hearing  (Fig.  7)  is  divided  into  three  portions: 

1.  The  external  ear. 

2.  The  middle  ear. 

3.  The  internal  ear  or  labyrinth. 

The  External  Ear. — This  consists  of  the  cartilaginous  structure 
that  is  commonly  called  the  "ear"  and  the  external  portion  of  the 
auditory  canal.  The  latter,  known  as  the  external  auditory  canal,  is 
about  one  inch  in  length  and  runs  inward  and  somewhat  forward.  It 
is  separated  from  the  middle  ear  by  the  tympanic  membrane  or  drum. 
Its  external  opening  is  termed  the  external  auditory  meatus. 

The  Middle  Ear. — This  extends  from  the  drum  to  the  internal  ear. 
It  approximates  one-sixth  of  an  inch  in  length  and  is  nearly  one-half 
an  inch  in  its  vertical  diameter.    In  this  cavity  are  the  three  ear  bones 


30 


ANATOMY  OF  THE  HEAD 


or  ossicles,  as  they  are  called.  The  middle  ear  is  in  communication 
with  the  mastoid  antrum  through  a  small  opening  and  with  the  naso- 
pharynx via  the  Eustachian  tube.  Through  the  middle  ear,  embedded 
in  its  mucous  membrane  lining,  passes  the  chorda  tympani  nerve,  a 
branch  of  the  facial,  on  its  way  to  join  the  lingual  branch  of  the  man- 
dibular nerve.  As  will  be  noted  later,  this  nerve  transfers  the  special 
sensations  of  taste  from  the  anterior  portion  of  the  tongue  to  the  brain. 
Hence  disease  of  the  middle  ear  may  be  attended  with  loss  of  the  sense 
of  taste  on  the  corresponding  side  of  the  tongue  owing  to  involvement 
of  this  nerve. 

Cartilage  of  auricula 
Attic 
Incus 

Malleus 

Tympanic  cavity 

Tensor  tympani 


Tympanic  membrane 


Cartilaginous 

part  of  ext. 

acoustic  meatus 


Bony  part  of 

ext.  acoustic 

meatus 


Fig.  7. — External  and  middle  ear,  opened  from  the  front.     Right  side.     (Gray.) 


The  Tympanic  Membrane  or  Drum. — This  consists  of  an  oval  mem- 
brane, obliquely  attached  to  the  sides  of  the  auditory  canal,  the 
upper  portion  being  nearer  the  external  opening.  It  presents  a  con- 
cave surface  to  the  exterior.  Between  its  layers  is  bound  the  "handle" 
of  the  malleus,  one  of  the  ossicles. 

The  Ear  Ossicles. — These  are  three  in  number  and  are  named  from 
without  inward,  the  malleus  or  hammer,  the  incus  or  anvil  and  the 
stapes  or  stirrup:  {a)  The  malleus  is  bound  to  the  drum  by  means 
of  its  handle  while  its  so-called  head  articulates  with  the  body  of  the 
incus.  (6)  The  incus  is  shaped  very  much  like  a  lower  molar  tooth  in 
that  it  has  two  root-like  processes  projecting  from  a  body.    The  body 


THE  EARS 


31 


articulates  with  the  malleus  and  the  longer  of  the  processes  with  the 
stapes,  (c)  The  stapes  on  the  one  hand  articulates  with  the  incus 
and  on  the  other  fits  into  the  oval  window  located  on  the  wall  of  the 
internal  ear.  These  bones  are  held  in  position  by  ligaments  that 
are  attached  to  the  wall  of  the  middle  ear.  The  fiittction  of  the  ear 
ossicles  is  to  transmit  and  magnify  the  sound  waves  received  by  the 
tympanic  membrane,  conveying  them  to  the  lymph  contained  within 
the  internal  ear. 

The  Mastoid  Antrum. — This  consists  of  a  moderately  large  cavity 
and  several  smaller  ones,  situated  within  the  mastoid  portion  of  the 
temporal  bone  just  behind  the  middle  ear  and  in  communication  with 
it.     These  air  cavities  are  often  the  seat  of  infection. 

The  Eustachian  Tube. — This  -canal  begins  at  the  anterior  end  of  the 
middle-ear  cavity,  passes  downward,  forward  and  somewhat  inward 
to  the  nasopharynx.  It  is  about  an  inch  and  a  half  in  length.  The 
function  of  the  Eustachian  tube  is  to  keep  the  air  within  the  middle 
ear  of  the  same  density  as  that  of  the  exterior.  This  prevents  any 
damage  to  the  drum  arising  from  inequality  of  air  pressure. 


Fig.  8. — Right  osseous  labyrinth.     Lateral  view.     (Gray.) 


The  Internal  Ear  or  Labyrinth  (Fig.  8)  .—This  consists  of  three  parts : 
The  vestibule. 
The  cochlea. 
The  semicircular  canals. 
Each  one  of  these  parts  is  made  up  of  bony  walls  enclosing  within 
them  a  membraneous  structure.     Separating  the  membraneous  por- 
tion from  the  bony  is  lymph  which  receives  the  name  of  'perilymph, 
while  within  the  membraneous  structures  is  more  lymph,  termed 
endolyviph. 

Of  the  three  parts  of  the  internal  ear,  the  cochlea  is  placed  anteriorly 
and  the  semicircular  canals  posteriorly,  while  the  vestibule  lies  between 
them  and  serves  as  a  connecting  chamber. 


82  ANATOMY  OF  THE  HEAD 

The  Vestibule. — In  the  external  wall  of  the  vestibule  is  the  oval 
window  into  which,  as  already  stated,  fits  the  base  of  the  stapes. 
The  vestibule  opens  into  the  cochlea  by  one  opening  and  into  the 
semicircular  canals  by  five  openings.  It  contains  two  membraneous, 
sac-like  structures,  the  utricle  and  the  saccule.  These  are  filled  with 
endolymph  and  are  connected  with  the  membraneous  portions  of  the 
semicircular  canals  and  cochlea.  In  the  utricle  are  also  found  many 
minute  calcareous  bodies  called  otoliths.  These,  by  shifting  their 
positions  under  varying  conditions,  transmit  impulses  to  the  nerve 
filaments  in  the  mucous  membrane  of  the  utricle. 

The  Cochlea. — This  in  structure  resembles  a  snail's  shell  and  from 
the  exterior  is  somewhat  cone-shaped.  It  is  placed  with  the  apex  out- 
ward. In  its  base  are  found  numerous  openings  through  which  the 
branches  of  the  auditory  nerve  pass.  The  base  measures  about  two- 
fifths  of  an  inch  in  diameter  and  the  height  of  the  structure  is  approxi- 
mately one-quarter  of  an  inch.  The  spiral  canal  within  the  cochlea 
makes  about  two  and  a  half  turns  around  the  central  axis.  This 
canal  is  divided  into  three  compartments  running  the  whole  length  of 
the  spirals.  In  the  median  compartment,  which  is  the  membraneous 
portion  of  the  cochlea,  is  the  organ  of  Corti,  the  name  given  the  structure 
which  receives  the  sound  waves  and  transmits  them  to  the  filaments 
of  the  auditory  nerve  ending  within  the  mucous  membrane  lining. 
This  compartment  is  filled  with  endolymph. 

The  Semicircular  Canals. — These  are  three  in  number  and  come  off 
from  the  posterior  aspect  of  the  vestibule.  They  are  so  located  as  to 
be  at  right  angles  with  one  another.  Two  are  in  the  vertical  plane 
and  one  in  the  horizontal.  Within  these  are  the  membraneous  semi- 
circular canals,  external  to  which  is  the  perilymph  and  within  which 
is  the  endolymph.  They  are  lined  with  a  special  form  of  epithelium, 
the  cells  of  which  are  in  intimate  relationship  with  the  end  filaments 
of  the  vestibular  branches  of  the  auditory  nerve.  These  canals 
undoubtedly  play  an  important  part  in  the  mechanism  concerned 
in  the  maintenance  of  the  equilibrium  of  the  body. 

Interconnection  of  the  Nerve  Supply  of  the  Ears  and  Teeth. — The  nerves 
to  the  ears  are  associated,  through  certain  ganglia,  i.  e.,  the  otic  and 
Meckel's,  with  the  nerves  that  supply  the  teeth.  Hence  it  is  not 
uncommon  to  have  earache  accompanied  by  toothache  or  vice  versa. 
At  times  earache  may  be  the  only  symptom  of  a  dental  lesion. 

THE  MOUTH. 

The  mouth  may  be  defined  as  the  cavity  at  the  beginning  of  the 
alimentary  canal.  It  contains  the  organ  of  mastication  and  is  intimate- 
ly connected  with  the  function  of  speech  and  the  special  sense  of  taste. 
It  is  bounded  in  front  by  the  lips;  laterally  by  the  cheeks;  above  by  the 
hard  and  soft  palates;  and  below  by  the  mylohyoid  and  genio-hyoid 
muscles  which  form  its  floor.     It  contains  the  teeth  and  the  tongue. 


THE  MOUTH 


33 


Anteriorly  the  mouth  opens  to  the  exterior  throuj^h  the  lips  and 
posteriorly  into  the  pharynx  throu^li  th(!  j'dvces.  The  mouth  cavity 
is  divided  into  two  portions:  (a)  the  vestibule,  which  lies  between  the 
lips,  cheeks  and  teeth,  and  (h)  the  mouth  i)roper  or  oral  cavity,  internal 
to  the  teeth.  It  is  lined  with  mucous  mernbraiu;  of  the  stratified 
squamous  variety.  This  membrane  contains  many  nniccjus  glands 
which  pour  their  contents  into  the  mouth. 

The  bony  framework  of  the  mouth  is  formed  by  (a)  the  su})erior 
maxillary  bones,  (h)  the  palate  bones,  and  (c)  the  inferior  maxillary 
bone  or  mandible. 


Med.  jM^'-  I'i'J.^ 


Dilatator  nauis  j'ostekior 


Incisive  fossa 


''\vK''--'       U  rhitul    S.U  rf  n  c  e  ^^  s,^'^, 


Alveolar  canals 


•;'-^W^""^      -•■■'i'l    Maxillqry  tuberosity 


Fig.  9. 


/'finolars 
Left  maxilla.     Outer  surface.     (Gray.) 


The  Superior  Maxillary  Bones  (Fig.  9). — These  are  two  in  number 
and  form  the  bulk  of  bone  below  the  forehead  exclusive  of  the  promi- 
nences of  the  cheeks.  Each  superior  maxilla  consists  of  a  body  and 
four  processes. 

The  Body. — On  the  anterior  surface  is  seen,  from  above  downward: 
(a)  a  portion  of  the  orbital  margin;  (6)  the  infra-orbital  foramen; 

(c)  incisive  fossa,  a  depression  above  the  roots  of  the  incisor  teeth; 

(d)  the  canine  fossa,  a  depression  behind  the  prominent  root  of  the 
cuspid  tooth,  and  (e)  the  ridges  of  bone  overlying  the  roots  of  the 
incisor  and  cuspid  teeth;  (/)  in  the  median  line  a  sharj)  process  of 
bone  called  the  nasal  spine. 

The  superior  surface  of  the  body  forms  a  portion  of  tlic  floor  of 


34  ANATOMY  OF  THE  HEAD 

the  orbit.  It  presents  the  inner  opening  of  the  infra-orbital  canal. 
From  this  canal  are  given  off  branch  canals  which  convey  the  blood- 
vessels and  nerves  to  the  anterior  teeth  and  bicuspids. 

The  posterior  surface  forms  part  of  the  zygomatic  fossa  and  pre- 
sents the  opening  of  the  posterior  dental  canals  that  take  the  blood- 
vessels and  nerves  to  the  molar  teeth. 

The  internal  or  nasal  surface  forms  a  portion  of  the  outer  wall  of 
the  nasal  cavity.  It  presents  the  opening  that  leads  into  the  maxil- 
lary sinus  or  antrum  of  Highmore.  This  large  air  cavity  is  situated 
within  the  body  of  the  superior  maxillary  bone  and  has  been  described 
under  the  heading  of  Sinuses. 

The  Four  Processes: 

1.  Nasal. 

2.  Malar. 

3.  Palate. 

4.  Alveolar. 

The  nasal  process  is  situated  between  the  nose  and  the  orbit,  pro- 
jecting upward  from  the  body  of  the  bone  and  articulates  with  the 
frontal  bone. 

The  malar  process  manifests  itself  on  the  outer  surface  of  the  bone 
and  articulates  with  the  malar  bone. 

The  palate  process  projects  horizontally  from  the  inner  surface  of 
the  body,  articulates  with  the  corresponding  process  of  the  superior 
maxillary  bone  of  the  opposite  side  and  thus  forms  with  its  supe- 
rior surface  the  anterior  portion  of  the  floor  of  the  nose  and  with  its 
inferior  surface,  the  corresponding  portion  of  the  roof  of  the  mouth. 

The  alveolar  process  is  built  up  on  the  lower,  outer  border  of  the 
body  for  the  purpose  of  supporting  the  teeth,  the  roots  of  which  are 
found  within  its  substance. 

The  Palate  Bones  (Fig.  10). — These  are  two  in  number.  In  form  they 
may  be  likened  to  the  letter  "L".  Their  upright  portion,  called  the 
vertical  plate,  helps  to  form  the  outer  wall  of  the  nasal  cavity.  The 
bone  corresponding  to  the  base  of  the  "L"  is  called  the  horizontal  plate 
and  articulates  anteriorly  with  the  palate  process  of  the  superior  max- 
illa, thus  aiding  in  the  formation  of  the  floor  of  the  nose  and  roof  of 
the  mouth.  Posteriorly  the  horizontal  plate  ends  in  a  free  border  to 
which  is  attached  the  soft  palate. 

The  Inferior  Maxillary  Bone  or  Mandible  (Fig.  11). — In  form  this 
bone  resembles  a  horseshoe  and  is  composed  of  a  body  and  two  rami. 
The  latter  arise  from  the  posterior  ends  of  the  body.  The  angle 
formed  between  the  rami  and  the  body  varies  in  degree  according  to 
race,  type  and  age.  The  mandible  is  the  only  bone  in  the  skull  that  is 
movable. 

The  Body. — The  external  surface  is  usually  concave  from  above 
downward,  and  ends  below  in  a  thick  ridge.  In  the  median  line  in 
front  is  another  thick  ridge  placed  at  right  angles  to  the  border.    This 


THE  MOUTH 


35 


receives  the  name  of  symphysis  menti.     Below,  this  fuses  with  the 
lower  border  of  the  bone  to  form  the  prominence  of  the  chin. 


Sfhe  nopalatine 
foramen 

Sphenoidal  process 
Articular  portion 

Non-articiilar 
portion 


Posterior 
nasal 
spine 


Pyrmnidal 
process 

Fig.  10. — Left  palatine  bone 


HORIZONTAL 
PART 


Posterior  aspect.     Enlarged.      (Gray.) 


itli^^. 


Mylohyoid  line 

BODY 

Fig.  11. — The  mandible.     Inner  surface.     Side  view.     (Gray.) 


Genio- 

glossus 
Genio- 

hyoideus 


In  the  region  of  the  first  and  second  bicuspid  teeth  and  about 
half-way  between  the  upper  and  lower  borders  of  the  bone  are  seen 
the  mental  j or amina,  one  on  either  side.    These  are  the  anterior  open- 


36  ANATOMY  OF  THE  HEAD 

ings  of  the  mandibular  canals  and  transmit  the  mental  vessels  and 
nerves.  The  alveolar  process  is  built  on  the  superior  border  of  the 
body  and  serves  to  maintain  the  lower  teeth  in  position. 

The  internal  surface  (Fig.  11)  presents  in  the  median  line  four 
tubercles  for  the  attachment  of  muscles.  Passing  back  from  these  along 
the  body  of  the  bone  and  half-way  between  its  borders  is  a  ridge  called 
the  mylohyoid  ridge.  This  serves  for  the  attachment  of  the  muscle 
of  the  same  name  which  forms  the  floor  of  the  mouth.  Above  this 
ridge  just  to  either  side  of  the  median  line  are  two  depressions  called 
the  sublingual  fossoe  and  resting  in  these  lie  the  sublingual  glands. 
Below  this  ridge  in  the  region  of  the  bicuspid  and  molar  teeth  on  either 
side,  are  two  other  depressions  that  receive  the  submaxillary  glands. 
The  sublingual  and  submaxillary  glands  pour  their  secretion  into  the 
mouth  through  a  common  duct,  Wharton's,  the  opening  of  which  is 
on  either  side  of  the  frenum  of  the  tongue. 

The  Rami. — The  external  surface  of  each  ramus  serves  for  the 
attachment  of  one  of  the  muscles  of  mastication,  the  masseter.  The 
'posterior  border  terminates  below  in  what  is  commonly  called  the  angle 
of  the  jaw.  The  internal  surface  serves  as  a  place  of  attachment  for 
certain  of  the  muscles  of  mastication,  i.  e.,  the  internal  pterygoid  and 
the  temporal.  This  surface  presents  about  at  its  midpoint  an  opening, 
the  inferior  dental  foramen,  which  leads  into  the  canal  of  the  same 
name.  It  transmits  the  inferior  dental  artery  and  nerve  which  furnish 
the  blood  and  nerve  supply  to  the  lower  teeth. 

The  superior  border  of  each  ramus  presents  two  prominences  between 
which  is  a  well-marked  notch.  The  anterior  prominence  is  called  the 
coronoid  process  and  serves  for  the  attachment  of  the  temporal  muscle. 
The  posterior  prominence  is  surmounted  with  an  articular  cartilage, 
receives  the  name  of  the  condyle,  and  enters  into  the  formation  of  the 
temporomaxillary  articulation.  To  the  internal  surface  of  the  condyle 
is  attached  the  external  pterygoid  muscle. 

The  Temporomaxillary  Articulation. — ^This  is  a  slidiDg  hinge  joint 
and  is  formed  by  the  glenoid  fossa  on  the  base  of  the  skull  and  the 
condyle  of  the  mandible.  The  glenoid  fossa  is  somewhat  cup-shaped 
and  is  limited  anteriorly  by  a  ridge,  the  eminentia  articularis.  This 
aids  the  ligaments  of  the  joint  in  restricting  the  forward  slide  of  the 
mandible.  The  articulating  surface  of  the  condyle  is  oblong  with  the 
long  diameter  in  the  transverse  plane.  Lying  between  the  condyle 
and  the  fossa  is  the  intra-articular  fibro-cartilage.  The  capsular  liga- 
ment encloses  the  entire  joint  in  a  fibrous  sheath.  Four  strong  fibrous 
ligaments  help  to  maintain  the  proper  position  of  the  condyle. 

The  Muscles  Active  in  Moving  the  Mandible. — ^These  may  be  divided 
into  two  sets:  (a)  the  so-called  "muscles  of  mastication"  which  bring 
the  lower  teeth  in  contact  with  the  upper  in  the  process  of  chewing 
by  raising  the  mandible  and  (6)  the  depressor  muscles  or  those  which 
pull  the  mandible  downward  as  in  opening  the  mouth, 


THE  MOUTH  37 

(a)  The  muscles  of  mastication  are  five  in  number,  i.  e.: 

Temporal. 

Masseter. 

Buccinator. 

Internal  pterygoid. 

External  pterygoid. 
(6)  The  depressor  muscles  are  also  five  in  number. 

Genio-hyoid. 

Genio-hyo-glossus. 

Mylo-hyoid. 

Digastric. 

Platysma  myoides. 
The  Lips  and  the  Cheeks  (Fig.  12). — These  structure  are  made  up  of 
muscles  and  fibro-elastic  tissue.  By  the  action  of  the  muscles  found  in 
the  lips  and  cheeks  are  produced  the  many  varied  facial  expressions 
giving  the  outward  manifestation  of  different  mental  states.  Hence 
these  muscles  are  known  as  the  muscles  of  expression.  The  lips  and 
cheeks  are  covered  on  the  external  surface  with  skin  and  on  their  inter- 
nal or  oral  surface  with  mucous  membrane.  These  two  coverings  unite 
at  the  outer  border  of  the  lips.  The  mucous  membrane  contains  many 
mucous  glands  which  pour  their  secretion  into  the  mouth  cavity.  In 
the  center  of  the  upper  lip  and  sometimes  of  the  lower  a  fold  of  mucous 
membrane  is  reflected  onto  the  alveolar  process.  This  is  called  the 
frenum. 

On  the  inside  of  the  cheek  about  opposite  the  upper  second  molar 
tooth  is  seen  a  small  papilla  which  marks  the  opening  of  the  duct 
leading  from  the  parotid  gland. 

The  Hard  Palate. — The  hard  palate  is  formed  by  the  palate  processes 
of  the  superior  maxillary  bones  and  the  horizontal  processes  of  the 
palate  bones.  Posteriorly  it  ends  in  a  free  border  to  which  the  soft 
palate  is  attached.  It  is  covered  with  mucous  membrane  the  surface 
of  which  anteriorly  is  thrown  into  folds,  called  rugcB. 

The  Soft  Palate. — This  structure  is  attached  to  the  posterior  border 
of  the  hard  palate  and  is  formed  by  five  different  muscles.  These 
are  in  turn  covered  with  mucous  membrane.  The  function  of  this 
structure  is  to  shut  off  the  nasal  passage  from  the  mouth  during  the 
act  of  swallowing. 

The  Mucous  Membrane. — The  mucous  membrane  or  lining  tissue  of 
the  mouth  is  made  up  of  two  layers,  the  epithelium  and  the  underlying 
connective  tissue  on  which  this  rests.  Beneath  these  two  layers  is 
the  suhviucosa  which  is  also  composed  of  connective  tissue. 

The  epithelium  is  of  the  stratified  squamous  variety  the  outer  cells  of 
which  become  cornified  and  scaly  on  that  part  overlying  the  alveolar 
process  and  the  hard  palate  (Fig.  13) .  Under  the  epithelium  is  a  layer  of 
fibro-elastic  tissue  the  outer  surface  of  which  is  surmounted  with  papillse 
that  extend  into  the  epithelium.  In  this  tissue  may  be  seen  the  ducts 
of  many  glands  which  are  passing  through  the  mucous  membrane  to 


38 


ANATOMY  OF  THE  HEAD 


reach  the  free  surface.  The  glands  themselves  are  located  in  the  sub- 
mucosa  which  is  composed  of  large  bundles  of  white  fibrous  connective 
tissue,  ably  supporting  the  mucous  membrane  and  richly  supplied 
with  bloodvessels  and  nerves.  The  glands  are  of  two  varieties,  serous 
and  mucous,  and  they  are  constantly  active. 


Mucous 
gland" 


Epifhelinm 
of  mucous, 
membrane 


Blood- 
vessels 


'/■'-t^Hair 

^     follicles 


Epidermis 


Epithelium 
of  mHCous-'\ 
membrane 

Cross  sections  /, 
of  muscle'"--. 


Longitudinal 
sections 
of  muscle 
fibres 


with  high' 
papillx  "" . 


/^  Place  where  stratum 
cornenm  begins 


Fig.  12. 


-Section  through  the  upper  lip  of  a  two-and-a-half-year-old  child. 
X    14.     (Szymonowicz.) 


The  Tongue.- — The  tongue  is  a  muscular  organ  composed  of  a  root, 
a  body  and  an  anterior  free  extremity  or  tip.  It  is  made  up  of  five 
muscles  and  is  covered  with  mucous  membrane.  The  under  sur- 
face is  attached  to  the  floor  of  the  mouth  by  a  fold  of  this  membrane 
called  the  frenum.  The  base  of  the  tongue  is  attached  to  the  hyoid 
bone  and  to  the  muscles  of  the  pharynx. 


THE  MOUTH 


39 


On  the  surface  of  the  tongue  are  seen  three  varieties  of  papilloB. 
These  are  composed  of  a  connective-tissue  core  developed  in  the 
corium  (tissue  unrler  the  epithelium)  and  covered  with  epithelium. 


Fig.   13. — Stratified  squamous  epithelium  covering  the  alveolar  process:     C,  corneous 
layer;  P,  papilla  of  connective  tissue.     About  400  X.     (Noyes.) 


s 

Fig.  14. — A  section  of  a  taste  bud:    p,  pore;  g,  gustatory  cells ;  ep,  epithelial  cells; 
.s,  sustentacular  cells;  h,  bristles  of  the  gustatory  cells.     (Schaefer.) 

The  most  important  of  these  papillse  are  situated  on  the  back  part 
of  the  tongue,  are  arranged  in  the  form  of  a  "V"  with  the  point  back- 
ward, are  eight  to  twelve  in  number  and  are  called  circumvallate  pap- 
illcB.     At  the  base  of  these  papillae  are  located  the  taste  buds  (Fig.  14), 


40  ANATOMY  OF  THE  HEAD 

specialized  bodies  in  which  filaments  of  the  glossopharyngeal  nerve  end 
and  through  which  media  the  sense  of  taste  is  active.  Probably  there 
are  also  some  taste  buds  in  the  anterior  portion  of  the  tongue  which 
are  innervated  by  branches  from  the  chorda  tympani  nerve  that  reaches 
the  tongue  by  joining  the  lingual  nerve  soon  after  it  branches  from  the 
mandibular  nerve. 

On  the  base  of  the  tongue,  behind  the  circumvallate  papillae,  is 
found  considerable  lymphoid  tissue.  This  is  given  the  name  of  the 
lingual  tonsil. 

The  nerve  supply  of  the  tongue  is  interesting  in  that  it  is  derived 
from  four  different  sources.  The  four  nerves  functionate  in  three  ways : 
(a)  The  nerves  of  special  sense  are  the  glossopharyngeal  and  the  chorda 
tympani.  (6)  The  nerve  of  common  sensation  is  the  fifth  cranial  or 
trifacial  and  (c)  the  motor  nerve  to  the  muscles  of  this  organ  is  the 
hypoglossal  or  twelfth  cranial. 

The  Nerve  and  Blood  Supply  of  the  Dental  Tissues. — The  nerve 
supply  to  the  structures  entering  into  the  formation  of  and  associated 
with  the  oral  cavity  is  mainly  through  the  trifacial  or  fifth  cranial  nerves 
and  the  facial  or  seventh  cranial  nerves.  Their  blood  supply  is  brought 
by  the  internal  maxillary  artery,  a  branch  of  the  external  carotid 
artery. 

The  Trifacial  or  Fifth  Cranial  Nerve  (Plate  I). — This  is  the  great 
sensory  nerve  of  the  head  and  face.  It  also  contains  a  few  motor 
fibers.  Its  connections  and  terminations  within  the  brain  substance 
are  very  extensive  and  far  too  intricate  to  be  detailed  in  a  work  of  this 
kind.  With  its  external  distribution,  however,  the  student  is  expected 
to  be  quite  familiar.  It  must  be  borne  in  mind  that  while  the  fibers  of 
the  nerve  are  described  anatomically  as  running  from  the  brain  to  the 
periphery,  yet  physiologically,  sensory  nerves  should  be  traced  in  just 
the  opposite  direction  because  they  carry  impulses  from  the  exterior 
to  the  centrally  located  ganglia. 

The  fifth  nerve  leaves  the  pons  Varolii  (a  portion  of  the  spinal  cord 
just  below  the  brain)  in  the  form  of  two  roots,  an  anterior  motor  and 
a  posterior  sensory.  The  latter  root  enters  a  large  ganglion,  the  Gas- 
serian,  situated  on  the  floor  of  the  middle  fossa  of  the  skull  just  behind 
the  foramen  ovale.  From  this  ganglion  three  large  trunks  are  given 
off  as  follows: 

The  ophthalmic  or  first  division. 

The  superior  maxillary  or  second  division. 

The  inferior  maxillary  or  third  division. 

The  ophthalmic  division  passes  forward  and  enters  the  orbit  through 
the  sphenoidal  fissure  supplying  the  various  structures  in  this  cavity, 
the  nasal  cavity  and  the  upper  part  of  the  face,  with  sensation. 

The  superior  maxillary  division  leaves  the  cranium  through  the 
foramen  rotundum  entering  the  sphenomaxillary  fossa.  From  this 
fossa  it  gains  entrance  to  the  orbit  via  the  sphenomaxillary  fissure. 
It  passes  along  the  floor  of  the  orbit  to  the  infra-orbital  canal  which 


PLATE    1 


Sensory  root 
Motor  root 


A  uriculotemporal' 
nerve 


Distribution  of  the  Maxillary  and  Mandibular  Nerves,  and 
the  Submaxillary  Ganglion.     (Gray). 


THE  MOUTH  41 

it  enters  and  then  emerges  from  the  canal  through  the  infra-orbital 
foramen  to  supply  the  tissues  of  the  face  in  the  region  of  this  opening. 
Just  before  this  division  enters  the  orbit  it  gives  off  the  posterior  superior 
dental  branches  that  supply  the  upper  molar  teeth.  These  reach  the 
teeth  by  passing  through  the  posterior  dental  canals,  the  entrance  to 
which  are  found  on  the  posterior  surface  of  the  superior  maxillary  bones. 
While  in  the  infra-orbital  canal  branches  are  given  off  that  supply  the 
upper  bicuspid,  cuspid  and  incisor  teeth. 

The  other  most  important  branches  of  the  superior  maxillary  division 
are  the  sphenopalatine  nerves  which  are  given  oft'  in  the  sphenomaxil- 
lary fossa.  These  pass  to  a  ganglion  also  situated  in  this  fossa  known 
as  the  sphenopalatine  or  Meckel's  ganglion.  They  constitute  the  sen- 
sory roots  of  this  structure.  It  also  receives  a  motor  root  that  comes 
indirectly  from  the  facial  nerve.  Meckel's  ganglion  is  of  importance 
to  the  student  of  oral  anatomy  because  its  branches,  which  are  numer- 
ous, are  distributed  to  the  mucous  membrane  of  the  sphenoidal  and 
ethmoidal  air  cells  and  nasal  cavity,  to  the  hard  palate,  the  soft  palate 
and  the  tonsils. 

There  are  no  motor  fibers  found  in  either  the  ophthalmic  or  superior 
maxillary  divisions  of  the  fifth  nerve.  Their  function  is  purely  a 
sensory  one,  that  of  touch  and  pain,  to  those  structures  to  which  they 
are  distributed. 

The  inferior  maxillary  division  emerges  from  the  cranium  through 
the  foramen  ovale.  Accompanying  it  through  this  opening  is  the  motor 
root  of  the  nerve  which  joins  the  sensory  division  just  outside  the 
cranium.  This  combined  trunk  is  now  located  in  the  zj'gomatic  fossa 
and  almost  immediately  is  found  to  divide  again.  One  of  these  divi- 
sions contains  nearly  all  of  the  motor  fibers  and  is  distributed  to  the 
muscles  of  mastication,  excluding  the  buccinator.  The  other,  contain- 
ing but  a  few  motor  fibers  and  made  up  mostly  of  sensory  ones,  is  the 
larger  of  the  two  and  divides  into  three  branches,  i.  e.,  (a)  the  auric- 
ulotemporal, which  supplies .  the  tissue  about  the  ear,  the  temporo- 
mandibular articulation  and  sends  communicating  branches  to  the  facial 
(seventh  cranial)  nerve;  (6)  the  lingual  which,  as  previously  stated, 
supplies  common  sensation  to  the  tongue  and  which  is  joined  by  the 
chorda  tympani  branch  of  the  facial  nerve;  and  (c)  the  inferior  dental 
nerve.  This  last  branch  enters  the  mandibular  canal  in  the  body  of 
the  inferior  maxillary  bone,  traverses  its  entire  length  and  emerges 
through  the  mental  foramen  as  the  mental  nerve  to  supply  sensation 
to  the  surrounding  tissues.  While  in  the  mandibular  canal  minute 
branches  are  given  off  to  the  various  lower  teeth. 

Just  as  the  inferior  dental  nerve  is  about  to  enter  the  mandibular 
canal  it  gives  off  quite  a  large  branch,  the  mylohyoid  nerve.  This 
contains  motor  fibers  and  passes  downward  to  supply  the  mylohyoid 
and  digastric  muscles. 

The  inferior  dental  nerve  also  sends  branches  to  two  ganglia,  the  otic 
and  the  submaxillary,  furnishing  them  with  their  sensory  roots.     The 


42  ANATOMY  OF  THE  HEAD 

most  important  nerves  coming  from  these  ganglia  are  secretory  branches 
to  the  saHvar}^  glands. 

The  Facial  or  Seventh  Cranial  Nerve. — This  is  the  great  moto7-  nerve 
of  the  head  and  face.  It  supplies  the  muscles  of  expression,  certain 
of  the  ear  muscles,  one  of  the  muscles  of  mastication,  the  buccinator, 
and  sends  communicating  branches  to  three  important  ganglia,  i.  e., 
the  otic,  the  submaxillary  and  Meckel's. 

The  facial  nerve  also  contains  a  few  sensory  fibers  that  convey  taste 
sensation  from  the  anterior  two-thirds  of  the  tongue. 

The  facial  nerve  emerges  from  the  pons  Varolii  and  enters  the  internal 
auditory  meatus  accompanying  the  auditory  nerve  and  artery.  It 
soon  leaves  the  auditory  canal  and  enters  another  bony  canal  known 
as  the  aqueductus  Fallopii  and  comes  out  on  the  exterior  of  the  skull 
through  the  stylomastoid  foramen.  It  then  enters  the  substance  of 
the  parotid  gland  and  breaks  up  within  this  structure  into  a  large 
terminal  arborization  known  as  the  pes  anserinus  (duck's  foot) . 

An  important  ganglion  is  situated  on  the  facial  nerve  within  the 
aqueductus  Fallopii  known  as  the  geniculate  ganglion.  From  this 
particular  part  of  the  nerve  important  branches  are  given  off  that 
communicate  with  Meckel's  ganglion,  the  otic  and  submaxillary 
ganglia  and  the  tympanic  plexus  of  nerves,  thus  connecting  the  seventh 
nerve  with  the  fifth  and  ninth  cranial  nerves.  This  fact  is  brought  out 
that  the  student  may  realize  how  closely  related  and  how  intimately 
interconnected  are  the  various  parts  of  the  cranial  anatomy.  Thus 
symptoms  manifested  in  one  area  may  be  but  transferred  sensations 
from  lesions  in  quite  remote  parts. 

One  of  the  most  important  branches  of  the  facial  nerve  is  the  ehordi 
tympani  (Plate  I).  This  is  given  off  in  the  aqueductus  Fallopii  and 
contains  mostly  sensory  fibers.  It  passes  through  the  middle  ear,  lying 
on  the  tympanic  membrane  under  the  mucous  membrane,  and  then 
escapes  from  this  cavity  through  a  small  canal,  entering  the  pterygo- 
maxillary  region.  It  passes  downward  and  forward  to  join  the  lingual 
branch  of  the  inferior  dental  nerve.  Its  sensory  fibers  pass  in  this  nerve 
to  the  tongue  and  supply  its  anterior  two-thirds  with  taste  sensation. 
The  motor  fibers  contained  in  the  chorda  tympani  are  passed  into 
the  otic  and  submaxillary  ganglia.  They  are  probably  the  source 
of  the  secretory  branches  given  off  from  these  ganglia  and  going  to 
the  salivary  glands. 

After  the  facial  nerve  leaves  the  stylomastoid  foramen  branches  are 
given  off  to  muscles  attached  to  the  temporal  bone  near  the  styloid 
process  and  about  the  external  auditory  meatus.  The  branches  form- 
ing the  terminal  arborization  supply  the  muscles  of  expression  situated 
about  the  eyes,  nose,  and  the  upper  and  lower  lips.  One  of  these 
branches  also  supplies  the  buccinator  muscle. 

The  Internal  Maxillary  Artery. — ^This  is  one  of  the  terminal  branches 
of  the  external  carotid  artery  and  arises  from  that  vessel  at  a  point 
just  below  and  internal  to  the  condyle  of  the  mandible.     It  embeds 


THE  MOUTH  43 

itself  deeply  in  the  substance  of  the  parotid  gland,  passes  internal  to 
the  ramus  of  the  jaw,  through  the  zygomatic  fossa  to  the  spheno- 
maxillary fossa.  From  here  it  is  continued  as  the  sphenopalatine 
artery  which  passes  into  the  nasal  cavity  through  the  sphenopalatine 
foramen. 

Important  Branches  of  the  Internal  Maxillary  Artery. — Soon  after 
its  origin  from  the  external  carotid,  the  internal  maxillary  artery 
gives  off  (a)  the  middle  meningeal  artery,  which  is  its  largest  branch. 
This  passes  upward  and  enters  the  cranial  cavity  through  the  foramen 
spinosum  and  supplies  the  whole  of  the  dura  mater  with  blood;  ih) 
the  mandibular  or  inferior  dental  artery,  that  passes  downward  in 
company  with  the  inferior  maxillajy  division  of  the  fifth  nerve  and 
enters  the  mandibular  canal.  It  gives  off  branches  to  the  lower  teeth 
as  it  passes  through  the  canal  and  then  emerges  on  to  the  chin  as  the 
mental  artery  through  the  foramen  of  the  same  name,  (c)  Branches 
to  the  muscles  in  the  maxillary  region  given  off  as  the  artery  traverses 
the  zygomatic  fossa,  {d)  In  the  sphenomaxillary  fossa  small  branches 
that  enter  the  posterior  dental  canals  in  the  posterior  portion  of  the 
superior  maxillary  bones  and  supply  the  upper  teeth,  (e)  The  infra- 
orbital artery,  which  enters  the  orbital  cavity  through  the  spheno- 
maxillary fissure  in  company  with  the  superior  maxillary  nerve.  It 
passes  forward  on  the  floor  of  the  orbit  and  enters  the  infra-orbital 
canal  to  emerge  on  the  face  through  the  infra-orbital  foramen.  While 
in  the  infra-orbital  canal,  it  gives  off  branches  that  supply  the  upper 
bicuspid,  the  cuspid  and  incisor  teeth.  (/)  The  descending  palatine 
artery  which  enters  the  posterior  palatine  canal  and  comes  out  on  the 
hard  palate  through  the  posterior  palatine  foramen  and  supplies  the 
hard  palate,  {g)  The  sphenopalatine  artery  which  is  the  terminal 
branch.  This  artery  enters  the  nasal  cavity  through  the  spheno- 
palatine foramen,  passes  forward  on  the  nasal  septum  and  then  dow'n- 
ward  to  emerge  on  the  hard  palate  through  one  of  the  foramina  found 
in  the  incisal  fossa.  It  is  then  known  as  the  naso-palatine  artery 
and  helps  supply  the  hard  palate,  anastomosing  with  the  descending 
palatine  artery. 

The  Lymphatics  of  the  Mouth. — The  mouth  is  well  supplied  with 
lymphatics  which  form  rich  networks  of  capillaries  in  the  mucous 
membrane.  These  capillaries  drain  into  larger  vessels  which  are 
connected  with  groups  of  lymphatic  glands.  Most  of  the  lymphatic 
vessels  from  the  mouth  proper,  i.  e.,  the  cavity  internal  to  the  teeth, 
empty  their  contents  into  the  cervical  lymphatic  glands.  Some, 
however,  from  the  lower  jaw  go  to  the  submaxillary  glands.  Those 
draining  the  vestibule  of  the  mouth  are  connected  with  the  sub- 
maxillary and  submental  glands.  These  in  turn  pass  their  contents  to 
the  cervical  lymphatic  vessels  and  glands. 

The  Salivary  Glands. — ^There  are  three  pairs  of  these  glandular  struc- 
tures, i.  e.:  (a)  parotid;  (b)  the  submaxillary;  and  (c)  the  sublingual. 

The  parotid  (near  the  ear)  glands,  one  on  either  side,  are  situated 


44  ANATOMY  OF  THE  HEAD 

below  and  in  front  of  the  ears  and  extend  from  the  zygoma,  above, 
to  the  angle  of  the  jaw,  below.  Their  ducts,  called  Steno's  or  Sten- 
son's,  open  into  the  mouth  at  points  about  opposite  the  upper  second 
molar  teeth. 

The  submaxillary  glands  are  situated  below  the  floor  of  the  mouth, 
in  contact  with  the  inner  surface  of  the  mandible  in  the  region  of  the 
bicuspid  and  molar  teeth.  The  ducts  from  these  glands  join  with  the 
ducts  from  the  sublingual  glands  and  make  their  entrance  into  the 
mouth  on  either  side  of  the  frenum  of  the  tongue.  These  ducts  are 
known  as  Wharton's. 

The  sublingual  glands  are  the  smallest  of  the  salivary  glands  and 
are  situated  above  the  floor  of  the  mouth,  in  the  sublingual  fossse  of 
the  mandible.  As  has  been  previously  stated,  their  ducts  join  with 
those  from  the  submaxillary  glands  and  make  their  entrance  into  the 
mouth  alongside  of  the  frenum  of  the  tongue. 

The  Fauces  and  the  Tonsils. — ^The  opening  leading  from  the  mouth 
to  the  pharynx  is  called  the  fauces.  It  is  bounded  above  by  the  soft 
palate,  below  by  the  base  of  the  tongue,  and  on  either  side  by  two 
pairs  of  muscles  which  receive  the  names  of  anterior  pillars  and  pos- 
terior pillars  of  the  fauces.  Between  these  two  pillars,  on  either  side, 
lie  the  faucial  tonsils.  These  are  lymph  nodes  which  probably  act 
as  filtering  plants  for  the  lymphatic  vessels  draining  the  mouth. 
Whatever  other  function  they  may  have  still  remains  a  mystery. 

There  are  two  other  masses  of  lymphoid  tissue  in  close  relationship 
to  the  mouth.  One  has  been  mentioned  under  the  description  of  the 
tongue.  This  is  called  the  lingual  tonsil.  The  other  is  known  as  the 
pharyngeal  tonsil  and  is  located  on  the  posterior  wall  of  the  pharynx, 
just  above  the  level  of  the  soft  palate  and  between  the  openings  of 
the  Eustachian  tubes.  Enlargement  of  the  pharyngeal  tonsil  often 
occurs  in  children.  The  growth,  commonly  known  as  adenoids,  so 
completely  fills  the  upper  portion  of  the  pharynx  as  to  shut  off  the 
passages  into  the  nose  and  the  child  is  forced  to  breathe  through  the 
mouth.  Mouth-breathing,  when  continued  for  some  time,  produces 
very  characteristic  symptoms  chief  among  which  is  a  severe  oral 
deformity.  Blocking  of  the  orifices  of  the  Eustachian  tubes  by  these 
growths  often  produces  impairment  of  hearing. 

THE  TEETH. 

The  teeth  may  be  defined  as  the  calcified  structures  attached  to 
the  jaw-bones  by  the  alveolar  processes  and  having  as  their  most 
important  function  the  breaking  up  of  food  material  in  preparation 
for  digestion. 

The  teeth  must  not  be  thought  of  as  a  part  of  the  osseous  system 
of  the  body  for  they  are  in  no  way  related  to  such  tissues  morpho- 
logically. Their  origin  and  structure  will  be  presented  in  detail  in 
Chapter  II. 


PLATE  II 


'^'■'i^-^ 


A  Diagram  of  a  Section    Through  an  Incisor.     (Noyes.) 

Showing  the  bloodvessels  of  the   pulp  and  peridental   membrane.      The  bone   is 
represented  as  much  too  dense. 


THE  TEETH  45 

The  teeth  make  their  appearance  in  two  series  or  sets.  The  first, 
known  as  the  deciduous  (falling  off),  temporary  or  mill:  teeth,  are 
twenty  in  number,  equally  divided  between  each  jaw,  and  named  as 
follows: 

Central  incisors. 

Lateral  incisors. 

Cuspids. 

First  molars. 

Second  molars. 
The  second  series  or  set,  known  as  the  permanent  teeth,  number 
thirty-two  when  complete.  The  increase  in  the  number  is  accounted 
for  by  the  following:  There  are  three  molars  on  each  side  in  the 
permanent  set  instead  of  two,  as  seen  in  the  deciduous.  Furthermore, 
these  are  all  three  erupted  behind  the  deciduous  molars.  The  latter 
are  replaced  when  shed  by  teeth  known  as  the  bicuspids.  It  is  there- 
fore to  be  noted  that  while  the  molar  teeth  in  the  deciduous  set  lie 
in  contact  with  the  cuspids,  the  molar  teeth  of  the  permanent  set 
are  separated  from  their  cuspids  by  two  teeth,  the  bicuspids.  The 
permanent  teeth  are  therefore  named  as  follows: 

Central  incisors. 

Lateral  incisors. 

Cuspids. 

First  bicuspids. 

Second  bicuspids. 

First  molars. 

Second  molars. 

Third  molars. 
Occlusion. — The  teeth  are  arranged  in  two  gracefully  curving  arches, 
the  lower  of  which  is  somewhat  the  smaller  so  that  the  upper  overlaps 
it.  The  teeth  of  one  arch  do  not  meet  those  of  the  other  in  an  end- 
to-end  arrangement,  but  are  dovetailed,  as  it  were,  between  each 
other.  This  brings  broad  surfaces  in  contact  instead  of  mere  points. 
There  are  over  one  hundred  of  these  surfaces  that  are  in  contact  when 
all  the  teeth  are  present  and  in  their  proper  position.  These  surfaces 
are  known  as  inclined  planes  and  it  is  the  sliding  together  of  these 
various  inclined  planes  in  a  scissors-like  action  that  properly  prepares 
the  food  for  digestion. 

The  normal  arrangement  of  the  inclined  planes  of  the  teeth  when 
the  jaws  are  closed  is  known  as  occlusion  or  normal  occlusion  (Fig.  15). 
In  this  arrangement  it  will  be  noted  that  every  tooth,  with  but  six 
exceptions,  is  in  contact  with  four  other  teeth,  i.  e.,  one  on  either  side 
of  it  and  two  in  the  opposing  arch.  The  teeth  excluded  from  this 
rule  are  the  lower  central  incisors  and  lower  third  molars  which  are 
in  contact  with  but  three  teeth,  and  the  upper  third  molars,  which 
are  in  contact  with  but  two  teeth. 

The  Anatomy  of  the  Tooth  (Plate  II). — A  tooth  is  divided  into  two 
parts,  the  crown  ancl  the  root,     The  crown  is  that  portion  that  projects 


46  ANATOMY  OF  THE  HEAD 

above  the  gum;  the  root  is  that  portion  that,  under  normal  conditions, 
is  surrounded  by  gum  and  alveolar  process.  The  bulk  of  the  tooth 
is  made  up  of  calcified  connective  tissue  called  dentin.  The  crown 
portion  of  the  dentin  is  covered  by  the  hardest  tissue  in  the  body,  i.  e., 
the  enamel.  This  is  of  epithelial  or  lining  tissue  origin.  The  root 
portion  of  the  dentin  is  covered  with  a  calcified  connective  tissue 
that  more  closely  resembles  bone  than  any  of  the  other  tooth  tissues. 
It  is  called  the  cementum.  It  slightly  overlaps  the  enamel  at  the  gum 
margin. 


1 

^H^^^^Kf 

^m       W'     m 

f^SBfm. 

fyy 

ISj 

WM 

^B  ^    1     1 

%M 

bf^P 

ll^^^lf^ 

^fllH 

fw 

^^ 

fi 

^■^^^ 

-^ 

.....^^ 

•  ;_B 

Fig.  15. — Normal  occlusion.     (Peeso.) 

In  the  center  of  the  dentin,  extending  the  whole  length  of  the  root 
and  more  or  less  into  the  crown,  is  a  cavity  called  the  pulp  cavity. 
This  contains  the  remains  of  the  organ  that  was  active  when  the 
tooth  was  being  formed  and  which  during  this  process  deposited  the 
dentin.     This  organ  is  called  the  pulp. 

The  pulp  cavity  is  divided  into  two  parts,  that  in  the  crown,  known 
as  the  pulp  chamber,  and  that  in  the  root  known  as  the  root  canal. 
The  root  canal  communicates  with  the  exterior  through  a  small  open- 
ing at  the  end  of  the  root.  This  opening  is  given  the  name  of  the 
apical  foramen.  Very  frequently  there  is  more  than  one  apical  fora- 
men present.  As  many  as  seven  or  eight  distinct  openings  have  been 
noted.  Through  the  apical  foramen  the  bloodvessels,  lymphatics 
and  nerves  pass  to  and  from  the  pulp. 


THE  TEETH  47 

Surrounding  the  root  and  separating  it  from  the  bony  wall  of  the 
socket  is  a  fibrous  membrane  known  as  the  peridental  membrane.  This 
has  for  its  most  important  function  the  binding  of  the  tooth  to  the 
surrounding  bone.  The  bone  that  supports  the  teeth  is  known  as 
the  alveolar  process.  This  is  formed  about  the  roots  of  the  teeth 
as  they  erupt.  When  a  tooth  is  removed  from  its  process  an  opening 
is  left  that  resembles  in  outline  the  shape  of  the  root.  This  cavity 
or  socket  is  called  an  alveolus. 

Surmounting  the  alv^eolar  process  is  a  dense,  fibrous  connective 
tissue  called  the  gum.  This  is  covered  with  mucous  membrane  con- 
tinuous with  that  of  the  rest  of  the  mouth. 

Nomenclature. 

The  following  terms  are  used  in  describing  the  anatomy  of  the  various 
teeth  and  the  student  will  find  it  necessary  to  become  familiar  with 
these  in  order  that  the  text  may  be  clear  and  the  parts  referred  to 
definitely  fixed  in  mind. 

The  neck,  cervix  or  gingival  margin  is  that  part  of  the  tooth  where 
the  enamel  and  cementum  meet. 

The  apex  is  the  end  of  the  root. 

The  occlusal  end  or  surface  is  the  top  of  the  crown,  /.  e.,  that  portion 
of  the  tooth  used  in  mastication. 

A  cusp  is  a  projection  or  tubercle  on  the  surface  of  the  crown. 

The  proximal  or  approximal  surface  is  that  surface  that  adjoins 
the  next  tooth.  The  most  prominent  point  of  this  surface  is  called 
the  point  of  contact  or  angle  of  the  tooth. 

The  mesial  surface  is  that  approximal  surface  that  is  nearest  the 
median  line  of  the  arch,  i.  e.,  a  line  drawn  between  the  central  incisors. 

The  distal  surface  is  that  approximal  surface  that  is  farthest  away 
from  such  a  line. 

The  surface  of  the  incisors  and  cuspids  that  presents  toward  the  lips 
is  called  the  labial  surface.  The  corresponding  surface  on  the  bicuspids 
and  molars,  presenting  toward  the  cheeks,  is  termed  the  buccal  surface. 

The  surface  of  the  upper  teeth  presenting  toward  the  palate  is 
called  the  palatal  surface.  The  corresponding  surface  on  the  lower 
teeth  presents  toward  the  tongue  and  is  called  the  lingual  surface. 
The  palatal  surface  of  the  upper  teeth  is  also  often  called  the  lingual 
surface. 

Descriptive  Anatomy  of  the  Various  Teeth. — The  Incisors  (Figs.  16  to 
19). — The  crowns  of  these  teeth  are  wedge-shaped  with  the  sharp  edge 
downward.  They  present  four  surfaces  and  an  incisal  or  cutting  edge 
for  study. 

Labial  Surface. — This  is  convex  and  on  the  upper  incisors  is  irregu- 
larly quadrilateral  while  on  the  lower  it  is  more  of  a  triangle  in  out- 
line. There  are  usually  two  grooves  running  vertically  through  this 
surface,  known  as  the  developmental  grooves.     AH  the  borders  of  this 


48 


ANATOMY  OF  THE  HEAD 


Fig.  16. — Left  upper  central  incisor.     Labial  surface.     (.Johnson.) 


Fig.  17. — Right  upper  lat- 
eral incisor;  lingual  ^^surface. 
(Johngon.) 


Fig.  18. — Right  lower 
central  incisor;  labial  sur- 
face.     (JohRSOR.) 


Fig.  19. — Right  lower 
central  incisor ;  lingual 
surface.     (Johnson.) 


Tim   I'KKT/f  49 

surface  are  more  or  less  convex,  that  at  the  gingivus  being  markedly 
so.  This  margin  also  ends  in  a  distinct  ridge.  The  mefilo-incisal 
angle  is  quite  sharp  while  the  dufto-incisal  angle  is  rounded. 

Lingual  or  Palatal  Surface. — This  is  irregularly  triangular  in  outline 
with  the  base  downward.  The  surface  is  concave  and  the  margins 
are  outlined  with  ridges.  Sometimes  in  the  center  of  the  cer\'ical 
ridge  is  a  rudimentary  cusp  at  the  base  of  which  is  a  depressitni  or  pit. 

Mesial  and  Distal  Surfaces. — In  outline  these  resemble  arrow  heads 
and  their  general  surface  is  convex.  They  present  two  concave  mar- 
gins, the  lingual  and  gingival,  and  one  convex,  the  labial. 

Incisal  Edge. — The  plane  of  this  surface  is  more  or  less  at  a  right 
angle  to  the  crown.  It  is  of  varying  thickness  and  in  newly  erupted 
teeth  presents  three  tubercles.  These  quickly  wear  off  as  the  teeth 
are  used. 

The  roots  are  cone-shaped  with  the  labiolingual  diameter  greater  than 
the  mesiodistal.  In  the  lower  teeth  the  roots  are  even  more  flattened 
mesiodistally  than  in  the  upper.  The  apex  of  the  root  often  has  a 
slight  distal  bend. 

Each  pulp  cavity  follows  roughly  in  outline  the  shape  of  the  tooth. 

Individual  Characteristics  of  the  Incisors. —  Upper  Central. — This  is 
the  largest  of  the  incisors.  Its  root  is  shorter  and  thicker  than  that  of 
the  others.  Upper  lateral.  The  distal  surface  of  the  crown  of  this 
tooth  is  very  convex  so  that  the  point  of  contact  is  quite  prominent 
and  the  incisal  edge,  oblique.  Its  root  is  the  longest  of  the  incisor 
roots.     Lower  Central.     This  is  the  smallest  of  the  incisors. 

The  Cuspids.  —  The  crowns  of  these  teeth  present  for  study  four 
surfaces  and  an  incisal  edge  that  takes  the  form  of  a  cusp. 

Labial  Surface  (Fig.  20) . — This  is  very  convex  and  is  marked  wuth  two 
developmental  grooves  between  which  is  a  prominent  ridge.  It  has 
five  borders  as  follows:  two  approximal,  two  incisal  and  one  cervical. 
The  approximal  and  the  cervical  are  convex,  while  the  incisal  are 
usually  quite  straight.  The  disto-incisal  border  is  the  longer  of  the 
two. 

Lingual  Surface  (Fig.  21) . — This  is  similar  in  outline  to  the  labial  and 
also  presents  a  vertical  ridge  running  through  the  center.  The  cervical 
end  of  this  ridge  is  frequently  marked  with  a  tubercle. 

The  mesial  and  distal  surfaces  are  similar  in  outline  to  the  corre- 
sponding surfaces  of  the  incisors  but  are  of  greater  dimensions  labio- 
lingually. 

The  Incisal  Edge. — ^This  is  in  the  form  of  two  planes,  a  mesial  and 
a  distal.  The  distal  is  the  longer  of  the  two.  At  their  point  of  union 
they  are  joined  by  the  labial  and  lingual  ridges  of  the  surfaces  of  the 
same  name,  to  form  the  cusjJ. 

The  roots  are  conical,  flattened  mesiodistally  and  sometimes  even 
concave  on  these  sides.  A  distal  bend  at  the  apex  is  quite  common. 
The  upper  cuspid  has  the  longest  root  of  any  tooth  in  the  mouth. 

Each  pulp  cavity  has  the  same  general  outline  as  the  tooth. 
4 


50 


ANATOMY  OF  THE  HEAD 


Distinguishing  Points  between  the  Upper  and  Lower  Cuspids. — The 
crown  of  the  lower  cuspid  is  more  dehcate  in  shape  and  shghtly  longer 
than  the  upper.  Its  root  is  shorter  and  more  flattened  mesially  and 
distally. 


Fig.  20. — Right  upper  cuspid;  labial  surface. 
(Johnson.) 


Fig.  21. 


—Right 
surface. 


upper   cuspid;   lingual 
(Johnson.) 


Mesial 


Fig.  22. — Left  upper  first  bicuspid;  occlusal  surface.     (Johnson.) 


The  Bicuspids  (Figs.  22  to  26). — The  crowns  of  these  teeth  are  irregu- 
larly cuboidal  in  form  and  present  five  surfaces  for  study,  i.  e.,  buccal 
lingual,  mesial,  distal  and  occlusal. 

The  buccal  surface  is  convex,  is  bounded  by  five  borders,  and  closely 
resembles  the  corresponding  surface  of  a  cuspid  but  is  somewhat 
shorter  than  this  tooth  in  its  vertical  dimension. 


THE  TEETH 


51 


Fig.  23.— Left  upper  first  bicuspid ;  mesial 
surface.     (Johnson.) 


Fig.  24. — Left  lower  first   bicuspid ; 
buccal  surface.      (Johnson.) 


Fig.  25. — Left  lower  first  bicuspid; 
distal  surface.     (Johnson.) 


Fig.  26. — Right  upper  second  bicuspid; 
mesial  surface.     (Johnson.) 


52  ANATOMY  OF  THE  HEAD 

The  lingual  surface  has  the  same  general  characteristics  as  the 
buccal  but  is  smaller  in  all  its  dimensions. 

The  mesial  surface  is  irregularly  quadrilateral  and  slightly  convex. 
Its  buccal  and  lingual  borders  are  convex,  the  lingual  being  consider- 
ably the  shorter  of  the  two.  The  cervical  and  occlusal  borders  are 
concave.  The  occlusal  border  of  the  upper  bicuspids  is  quite  "V" 
shaped,  the  apex  of  the  "V"  being  between  the  cusps. 

The  distal  surface  closely  resembles  the  mesial  but  is  much  more 
convex. 

Occlusal  Surface  (Fig.  22). — The  outline  of  this  surface  on  the  upper 
bicuspids  is  somewhat  egg-shaped  while  on  the  lower  bicuspids  it  is 
more  circular  in  form.  It  presents  for  study  two  cusps,  a  central  groove 
and  a  mesial  and  distal  border.  The  cusps  are  placed  buccally  and 
lingually,  the  buccal  being  the  larger  one.  Each  cusp  has  four  inclines 
or  inclined  planes,  as  they  are  usually  called.  These  are  named  from 
the  surface  toward  which  they  slope,  i.  e.,  mesial,  distal,  buccal  and 
lingual.  The  groove  runs  mesiodistally  and  separates  the  cusps.  The 
mesial  border  is  nearly  straight  while  the  distal  border  is  decidedly 
convex.     Both  of  these  borders  are  surmounted  with  ridges. 

The  Roots. — The  upper  first  bicuspid  has  two  roots.  Of  these  the 
buccal  is  the  larger.  All  the  other  bicuspids  have  but  one  root.  The 
buccolingual  dimension  of  the  root  is  the  greater.  Its  mesial  and 
distal  sides  are  concave.  A  distal  curve  to  the  apex  of  the  root  is 
common. 

The  Pulp  Cavity. — The  pidp  chamber  can  be  more  readily  outlined 
in  the  bicuspids  than  in  the  incisors  or  cuspids.  Its  form  follows 
roughly  that  of  the  crown  while  the  shape  of  the  pidp  canal  corre- 
sponds to  that  of  the  root.  The  upper  first  bicuspids  have  two  pulp 
canals,  the  other  bicuspids  usually  have  but  one,  although  two  may  be 
found. 

Individual  Characteristics  of  the  Bicuspids. — The  upper  first  is  the 
largest  of  the  bicuspids.     It  has  two  roots  and  two  root  canals. 

The  lower  first  is  the  smallest  of  the  bicuspids.  Its  lingual  cusp  is 
very  rudimentary.  Its  root  is  broad  mesiodistally  on  the  buccal  side 
and  quite  narrow  on  the  lingual  side. 

The  Upper  Molars  (Figs.  27  to  29). — The  crowns  of  these  teeth  are 
irregularly  cuboidal,  presenting  the  same  five  surfaces  for  study  as  do 
the  bicuspids.  The  crowns  of  the  molars  are  smaller  in  diameter  at 
the  neck  than  at  their  occlusal  border. 

The  buccal  surface  is  generally  convex  and  is  divided  vertically  by 
a  groove.  Often  in  the  center  of  this  surface  is  a  pit.  When  this  is 
present  the  buccal  groove  usually  terminates  in  it.  The  buccal  sur- 
face has  four  borders.  Of  these  the  occlusal  is  the  most  striking  in 
that  it  is  marked  with  two  cusps. 

The  lingual  surface  resembles  the  buccal  very  closely  except  that 
the  mesial  and  distal  margins  converge  more  at  the  cervix  as  they 
are  continued  into  one  root  instead  of  two  as  is  the  case  with  the 
corresponding  margins  of  the  buccal  surface. 


THE  ti<:i<:tii 


Fig.  27. — Left  upper  first  molar;  buccal  surface.     (Johnson.) 


Lingual 


Fig.  28. — Left  upper  first  molar;  occlusal 
surface.     (Johnson.) 


Fig.  29. — Left  upper  second  molar; 
lingual  surface.     (Johnson.) 


54  ANATOMY  OF  THE  HEAD 

The  mesial  surface  at  the  occlusal  third  is  convex  while  the  gingival 
two-thirds  is  straight  or  concave. 

The  distal  surface  is  similar  to  the  mesial,  though  perhaps  in  general 
a  little  more  convex. 

The  occlusal  surface  is  irregularly  rhomboidal,  the  acute  angle 
being  the  mesiobuccal  and  the  distolingual.  It  presents  four  cusps, 
two  of  which  are  buccal,  called  the  mesiobuccal  and  distobuccal  cusps, 
and  two  lingual,  called  the  mesiolingual  and  the  distolingual  cusps. 
The  mesiolingual  is  the  largest  cusp.  Running  obliquely  across  the 
occlusal  surface  there  is  in  succession  a  groove,  a  ridge,  and  a  second 
groove.  The  first  groove  begins  in  the  middle  of  the  mesial  margin, 
and  passes  distally  and  buccally  across  the  occlusal  surface  to  the  inter- 
val between  the  two  cusps  where  it  is  continued  over  on  to  the  buccal 
surface  as  the  buccal  groove.  The  ridge  runs  from  the  mesiolingual 
cusp  to  the  distobuccal  cusp.  The  second  groove  begins  between  the 
two  lingual  cusps  as  a  continuation  of  the  lingual  groove  and  runs 
distally  and  buccally  to  the  center  of  the  distal  margin.  Just  mesial 
and  distal  to  the  center  of  the  oblique  ridge  are  fossce. 

The  Roots. — These  are  three  in  number,  two  being  placed  buccally 
and  one  lingually.  The  lingual  is  the  largest  root  and  the  distobuccal 
the  smallest.  The  apices  of  the  two  buccal  roots  tend  to  converge 
toward  each  other. 

The  Pulp  Cavity. — The  outline  of  the  pulp  chamber  resembles  the 
form  of  the  crown.  On  the  floor  of  this  chamber  are  three  openings 
leading  into  the  three  root  canals. 

Individual  Characteristics  of  the  Upper  Molars. — The  first  molar  is  the 
largest  of  the  upper  molars.  It  is  often  distinguished  by  the  fact  that 
it  has  a  fifth  cusp  situated  at  the  mesio-occlusal  corner  of  the  lingual 
surface.  This  is  very  small  and  rudimentary.  The  roots  of  the  first 
molar  are  usually  larger  and  diverge  from  one  another  to  a  greater 
degree  than  in  the  other  upper  molars. 

The  second  molar  is  often  quite  flattened  mesiodistally.  It  never  has 
the  fifth  cusp.     Frequently  the  buccal  roots  show  a  distal  inclination. 

The  third  molar,  with  the  lower  third  molar,  is  the  most  variable 
tooth  in  the  head.  If  typical  it  should  present  but  three  cusps,  the 
distolingual  being  lost.  It  has  no  oblique  ridge,  but  presents  instead 
a  central  fossa.  There  may  be  three  roots  or  there  may  be  but  one, 
and  the  root  canals  vary  with  the  number  and  position  of  the  roots. 

The  Lower  First  Molar  (Fig.  30). — ^The  crown  of  this  tooth  is  also 
irregularly  cuboidal,  and  presents  five  surfaces  for  study. 

The  buccal  surface  differs  from  the  buccal  surface  of  the  upper 
molars  in  that  it  is  longer  mesiodistally  and  presents  two  grooves 
instead  of  one.  Its  occlusal  border  is  surmounted  by  three  cusps 
instead  of  two. 

The  lingual,  mesial  and  distal  surfaces  all  resemble  the  corresponding 
surfaces  of  the  upper  first  molar. 

The  Occlusal  Surface  (Fig.  31). — ^This  differs  considerably  from  the 


THE  TEETH 


55 


corresponding  surface  of  the  upper.    It  is  a  trapezoidal  in  outline  with 
the  long  side  buccally  and  is  marked  with  five  cusps,  five  grooves  and 


Fig.  30. — Right  lower  first  molar;  buccal  surface.      (Johnson.) 

a  central  fossa.    The  cusps  are  arranged  three  buccally,  named  from 
mesial  to  distal,  mesiobuccal,  buccal  and  distobuccal;  and  two  lin- 

Lingual 


Fig.  31. — Right  lower  first  molar;  occlusal  surface.     (Johnson.) 

gually,  named  mesiolingual  and  distolingual.     The  grooves  radiate 
from  the  central  fossa  and  are  named  mesial,  buccal,  distobuccal 


56 


ANATOMY  OF  THE  HEAD 


(between  the  buccal  and  distobuccal  cusps),  distal  and  lingual.  The 
mesiobuccal  cusp  is  the  largest  and  the  distobuccal  the  smallest. 

The  Roots. — These  are  two  in  number  and  are  placed  one  mesially 
and  the  other  distally  and  are  known  by  these  names.  They  present 
a  distal  inclination.     The  mesial  root  is  the  larger. 

The  Pulp  Cavity. — The  pulp  chamber  resembles  in  outline  the  crown. 
The  pulp  canals  are  frequently  three  in  number  there  often  being  two 
in  the  large  mesial  root. 

The  Lower  Second  Molar  (Fig.  32). — This  resembles  the  first  lower 
molar  but  is  a  smaller  tooth  and  has  but  four  cusps,  the  distobuccal 
being  absent.  The  cusp  corresponding  to  the  buccal  cusp  of  the  first 
molar  receives  the  name  of  distobuccal  in  the  second  molar. 


Fig.  32. — Right  lower  second  molar;  lingual  surface.     (Johnson.) 


The  occlusal  surface  presents  a  central  fossa  and  four  grooves  radiat- 
ing from  it. 

The  roots  are  somewhat  smaller  and  are  situated  close  together. 
But  two  root  canals  is  the  usual  order.  The  roots  have  a  marked  distal 
inclination. 

The  Lower  Third  Molar. — This  is  extremely  variable  in  form  but 
when  tj-pical  should  resemble  the  second  molar  in  miniature. 

Descriptive  Anatomy  of  the  Deciduous  Teeth. — The  deciduous  teeth 
resemble  the  permanent  teeth  in  their  general  form  but  are  of  course 
much  smaller.     Their  cusps  are  not  as  well  defined  and  the  form  of  the 


THE  TEETH  57 

molars  and  cuspids  is  such  that  they  are  larger  at  the  neck  than  at  the 
occlusal  border. 

The  incisors  and  cuspids  are  ver}'  much  like  the  corresponding 
teeth  in  the  permanent  denture;  the  lower  first  molars  quite  closely 
resemble  the  lower  second  permanent  molars;  the  second  molars, 
both  upper  and  lower,  are  similar  in  design  to  the  upper  and  lower 
first  permanent  molars;  the  uy per  first  molars,  however,  are  different 
in  certain  respects  from  any  of  the  other  teeth  and  therefore  require 
a  more  detailed  description. 

The  Upper  First  Deciduous  Molar. — The  occlusal  surface  presents 
three  cusps,  two  buccally  and  one  lingually.  The  latter  is  so  large, 
however,  that  it  makes  this  side  about  as  long  mesiodistally  as  the 
buccal.  This  surface  presents  a  central  fossa  with  three  grooves 
radiating  from  it,  i,  e.,  a  mesial,  a  buccal  and  a  distal. 

The  buccal  surface  resembles  that  of  any  upper  molar;  the  lingual 
is  very  convex  and  has  no  groove;  the  mesial  and  distal  are  convex 
at  their  cervical  borders. 

Approximate  Age  at  which  the  Various  Teeth  Erupt. — Lower  teeth 
erupt  before  the  upper  as  a  rule. 

The   Deciduous   Denture. 

Central  incisors,  6th  to  8th  month. 
Lateral  incisors,  8th  to  10th  month. 
First  molars,  10th  to  16th  month. 
Cuspids,  16th  to  20th  month. 
Second  molars,  20th  to  30th  month. 

The  Permanent  Denture. 

First  molars,  5th  to  7th  year. 
Central  incisors,  6th  to  8th  year. 
Lateral  incisors,  7th  to  9th  year. 
First  bicuspids,  8th  to  10th  year. 
Lower  cuspids,  9th  to  11th  year. 
Second  bicuspids,  10th  to  12th  year. 
Upper  cuspids,  11th  to  13th  year. 
Second  molars,  12th  to  14th  year. 
Third  molars,  17th  year  to  any  time  later. 


CHAPTER  II. 

HISTOLOGY  OF  THE  TEETH  AND  ASSOCIATED 
STRUCTURES.! 

By  ROBERT  H.  W.  STRANG,  M.D.,  D.D.S. 

The  Enamel.— This  is  the  only  calcified  tissue  in  the  body  that  is 
derived  from  epithelial  structures.  All  others  have  their  origin  in  con- 
nective tissue.  Enamel  is  also  the  hardest  of  the  tissues  and  contains 
no  organic  matter.  Chemically  it  is  made  up  for  the  most  part  of 
phosphate  and  carbonate  of  lime.  As  there  is  no  organic  matter  to 
be  found  in  its  make-up  it  must  be  designated  as  a  dead  tissue.  The 
epithelial  cells  that  are  active  in  its  formation  are  destroyed  when 
their  work  is  finished.  Owing  to  the  fact  that  enamel  is  of  epithelial 
origin  any  diseases  that  have  among  their  symptoms  eruptions  of  the 
skin,  such  as  the  various  contagious  fevers  of  childhood,  may  produce 
a  disturbance  of  enamel  formation  if  the  attack  comes  at  the  age  when 
this  tissue  is  being  laid  down.  This  accounts  for  many  of  the  cases  of 
pitted  and  poorly  formed  enamel  seen  on  the  permanent  incisor  teeth. 

Enamel  is  composed  of  two  structural  elements :  (a)  Enamel  prisms 
or  rods,  and  (6)  a  cementing  substance. 

The  Enamel  Rod  (Fig.  33). — These  are  prismatic  in  form,  having 
five  or  six  sides  and  their  average  diameter  is  about  one-half  that  of 
a  red  blood  corpuscle.  Throughout  their  entire  length  we  find  them 
alternately  constricted  and  expanded.  When  placed  side  by  side 
these  expansions  and  constrictions  are  not  dovetailed  into  each  other, 
but  are  arranged  opposite  one  another. 

The  Cementing  Substance.- — Between  the  rods  and  filling  up  the 
spaces  made  by  this  peculiar  arrangement  of  the  prisms,  is  the  cement- 
ing substance.  This  cementing  substance  is  also  highly  calcified  but 
is  more  susceptible  to  injury  than  the  prisms.  When  enamel  cracks 
the  line  of  cleavage  runs  through  the  cementing  substance  and  not 
across  the  rods.  When  an  acid  is  brought  in  contact  with  the  enamel 
the  cementing  substance  is  destroyed  before  the  rods. 

The  enamel  is  formed  from  within  outward  so  the  enamel  on  the 
surface  of  the  tooth  is  the  last  to  be  laid  down.  The  prisms  extend 
from  the  dentin  outward  and  are  arranged  in  a  manner  that  will 
best  resist  the  force  that  is  brought  upon  them  as  the  teeth  are  used. 
The  prisms  do  not  always  run  in  a  straight  line  from  the  dentin  to 
the  surface  but  in  many  places,  especially  where  the  stress  is  great, 

1  A  resume  from  Dental  Histology  and  Embryology  by  Dr.  F.  B.  Noyes. 


The  MameL 


59 


such  as  on  tlie  cusps  of  the  teeth,  they  are  intertwined  with  one  anotlier 
something  like  the  strands  of  a  rope.  Such  enamel  is  called  gnarled 
enamel.  Straight  enamel  is  that  in  which  the  prisms  run  in  practically 
a  straight  line  from  the  dentin  to  the  surface. 

In  sections  of  enamel  two  kinds  of  markings  are  distinguished  on 
the  cut  surface:  (a)  striation  and  (b)  stratification  (Fig.  34).  The 
striation  is  quite  like  that  of  voluntary  muscle  fibers  and  is  due  to 
the  alternating  expansion  and  contraction  segments  of  the  rods.  The 
stratificatio7i  is  seen  in  longitudinal  sections  only.  It  consists  of  dark 
bands  running  through  the  enamel.  These  bands  are  also  called  the 
Bands  of  Retzius  from  the  man  who  first  discovered  them.  They  are 
due  to  pigment  being  deposited  in  the  enamel  as  it  is  formed.     A  portion 


Fig.  33. — Enamel  rods  in  thin  etched  section.     (About  800  X.)     (Noyes.) 

of  the  enamel  having  been  formed,  upon  the  surface  of  this  is  deposited 
pigment.  Following  this  another  layer  of  enamel  is  laid  down  upon 
which  is  deposited  more  pigment,  etc.  These  lines  of  stratification  are 
therefore  an  index  as  to  just  how  the  enamel  is  laid  down  and  show  that 
the  first  layer  is  deposited  at  the  occlusal  end  of  the  crown  and  suc- 
cessive layers  work  their  way  rootward. 

When  a  tooth  first  erupts  it  is  covered  with  a  thin  membrane  called 
Nasmyth's  membrane.  This  is  the  remains  of  the  enamel  organ,  active 
during  the  formation  of  this  tissue.  It  soon  wears  off  as  the  tooth  is 
brought  into  use. 

White  or  mottled  spots  are  often  seen  in  enamel.  These  are  due  to 
the  fact  that  the  cementing  substance  has  not  been  deposited  between 


60 


HISTOLOGY  OF  THE  TEETH 


the  rods  in  these  areas.  The  air  spaces  left  by  this  failure  cause  a 
difference  in  light  refraction  and  make  the  spot  appear  opaque  or  whiter 
than  the  surrounding  tissue. 

Functions  of  the  Enamel. — (a)  It  covers  the  exposed  portion  of  the 
tooth  and  prevents  irritation  of  the  underlying  sensative  dentin. 

(6)  By  its  hardness  it  resists  abrasion  from  the  force  of  mastication. 
Enamel  differs  from  any  other  calcified  tissue  in  the  following  details: 

{a)  It  is  formed  by  epithelial  cells. 

(6)  It  contains  no  organic  material  either  in  the  form  of  cells  or 
intercellular  substance. 


Fig.  34. — Enamel  showing  both  striation  and  stratification.    (About  80  X.)    (Noyes.) 


(c)  The  organ  that  forms  it  disappears  after  its  work  is  complete. 

{d)  It  is  made  of  prisms  cemented  together.  All  other  calcified 
tissue  has  fibrous  connective  tissue  as  its  structural  basis. 

The  Dentin  (Fig.  35). — Dentin  is  a  calcified  connective  tissue  and 
is  used  to  make  up  the  bulk  of  the  tooth.  It  contains  considerable 
organic  matter  and  yields  gelatin  when  boiled.  Its  inorganic  matter  is 
mostly  carbonate  and  phosphate  of  lime. 

Structurally  dentin  is  made  up  of  the  following  elements : 

(a)  Dentin  matrix. 

(6)  The  dentinal  tubules  with  their  walls  which  latter  structures 
are  known  under  the  name  of  the  "sheaths  of  Neuman." 

(c)  The  dentinal  fibrils. 


THE   DENTIN 


61 


Fig.    35. — Dentin  showing  tubules  in  cross-section:     Dt,   dentinal  tubules;  D,  dentin 
matrix;  S,  shadow  of  sheaths  of  Newman.     (About  1150  X.)     (Noyes.) 


Fig.  36, — Dentin  at  dento-enamel  junction,  showing  tubules  cut  longitudinally. 
(About  760  X.)     (Noyes.) 


62  HISTOLOGY  OF  THE  TEETH 

The  Dentin  Matrix. — This  is  a  homogeneous  material  that  is  very 
elastic.  As  seen  with  the  unaided  eye  it  is  yellowish.  It  is  composed 
of  about  one-third  organic  material  and  two-thirds  inorganic  in  the 
form  of  lime  salts. 

The  Dentinal  Tubnles. — Extending  throughout  the  matrix  and  radi- 
ating from  the  pulp  cavity  are  minute  tubes.  These  take  a  spiral 
course  in  their  passage  through  the  matrix.  They  also  intercommuni- 
cate with  one  another.  They  end  at  the  dento-enamel  or  dento- 
cemental  junction.  At  the  former  junction  they  branch  close  to  their 
termination  in  delta-like  formations  (Fig.  36).  These  deltas  are  in 
communication  with  one  another.  This  intimate  interconnection  of 
many  tubules  explains  why  the  dento-enamel  junction  is  such  a  sensitive 
area  under  the  action  of  instruments.  At  the  dento-cemental  junction 
the  tubules  open  into  spaces  lying  between  the  cementum  and  the 
dentin.  These  spaces,  ranging  as  they  do  along  the  whole  length  of  the 
root,  form  what  is  known  as  the  "granular  layer  of  Tomes"  (Fig.  37). 
Although  several  investigators  have  claimed  that  they  have  found 
communicating  channels  between  the  granular  layer  of  Tomes  and  the 
canaliculi  of  the  cementum,  Dr.  Noyes  states  very  definitely  that  he 
has  never  been  able  to  demonstrate  this  fact. 

The  matrix  immediately  surrounding  the  tubules  is  of  a  more  dense 
composition  than  that  in  other  parts.  This  densely  formed  portion 
receives  the  name  of  the  sheath  of  Neuman.  The  name  is  somewhat 
misleading  for  it  is  not  a  true  membrane,  but  is  undoubtedly  a  special- 
ized portion  of  the  matrix  itself  forming  a  wall,  as  it  were,  to  the  tubes. 
It  has  been  found  that  the  sheaths  of  Neuman  have  considerable 
elastin  as  one  of  their  component  elements. 

The  Dentinal  Fibrils. — These  are  the  protoplasmic  processes  found  in 
the  tubules  and  are  extensions  from  the  cells  of  the  pulp  that  were 
active  in  the  formation  of  the  dentin.  These  cells  are  called  odonto- 
blasts. 

Function  of  the  Dentin. — (a)  Forms  the  great  bulk  of  the  tooth. 

(b)  Acts  as  an  elastic  cushion  to  the  enamel  so  that  this  tissue  will 
not  break  under  stress. 

(c)  Gives  strength  to  the  whole  tooth. 

The  Cementum  (Fig.  37). — This  is  also  a  calcified  connective  tissue. 
It  more  nearly  resembles  bone  than  does  the  dentin.  It  is  arranged 
in  consecutive  layers  around  the  tooth  root  and  slightly  overlaps  the 
enamel  at  the  cervical  margin. 

Structurally  cementum  is  made  up  of  the  following  elements : 

(a)  The  lamellae. 

(b)  The  lacunae  from  which  radiate  the  canaliculi. 

(c)  Cement  cells  or  corpuscles. 

(d)  The  embedded  fibers  of  the  peridental  membrane. 

The  LamelloB. — This  is  the  name  given  to  the  layers  of  cementum. 
These  vary  in  thickness  according  to  the  position  on  the  root,  being 
thinnest  at  the  gingival  margin  and  thickest  at  the  apex.    They  are 


THE  CEMENTUM 


63 


arranged  concentrically  about  the  root.  There  is  a  continuous  forma- 
tion of  cementum  going  on  throughout  life  so  that  the  older  the  indivi- 
dual, the  more  layers  of  cementum  there  will  be.  By  virtue  of  this 
property  of  continuous  formation  the  cementum  is  the  one  tissue  of 
the  tooth  that  is  capable  of  repairing  itself  after  injury.  Destruction 
of  the  dentin  on  the  surface  of  the  root  may  also  be  repaired  by  the 
cement  cells  filling  in  such  areas  with  cementum. 


Fig.  37. — Two  fields  of  cementum  showing  penetrating  fibers:  GT,  granular  layer 
of  Tomes;  C,  cementum  not  showing  fibers;  F,  penetrating  fibers.  (About  54  X.) 
(Noyes.) 


The  Lacunoe. — ^The  lacunse  are  minute  spaces  scattered  throughout 
the  cementum,  being  both  in  the  substance  of  the  lamellse  and  between 
the  various  layers.  From  these  radiate  in  all  directions  minute  canals 
called  canaliculi.  These  canaliculi  intercommunicate  with  those 
from  the  adjacent  lacunae.     The  cement  cells  or  corpuscles  lie  in  the 


64  HISTOLOGY  OF  THE  TEETH 

lacunae.     They  are  the  cells  that  are  active  in  the  formation  of  cemen- 
tum.     Their  protoplasmic  processes  extend  into  the  canaliculi. 

The  Embedded  Fibers  of  the  Peridental  Membrane. — ^The  cement 
cells  previous  to  the  formation  of  cementum  are  located  in  the  mem- 
brane that  surrounds  the  root,  the  peridental  membrane.  The  cement 
is  built  from  within  outward,  i.  e.,  that  nearest  the  dentin  is  the  first 
to  be  formed.  As  these  cells,  called  cementoblasts  when  active,  form 
the  various  lamellae  they  build  themselves  into  the  structure  that  they 
are  forming.  In  this  process  many  of  the  fibers  of  the  peridental 
membrane  are  also  built  into  the  cementum  and  after  a  time  become 
more  or  less  calcified.     These  constitute  the  embedded  fibers. 

On  the  opposite  side  of  the  peridental  membrane,  i.  e.,  that  side 
that  is  in  relationship  to  the  bone  of  the  alveolus,  we  find  that  fibers 
of  the  membrane  are  similarly  built  into  the  bone.  Through  the  agency 
of  all  these  embedded  fibers  the  tooth  is  firmly  held  in  its  socket. 

The  Function  of  the  Cementum. — It  is  the  tissue  which  through  its 
ability  to  attach  the  tooth  to  the  surrounding  connective  tissue,  holds 
it  in  position.  The  cementum  may  therefore  be  considered  as  the 
most  important  of  the  tooth  tissues. 

The  Pulp. — This  is  the  structure  occupying  the  cavity  within  the 
dentin.  It  represents  the  remains  of  the  organ  that  was  active  when 
the  dentin  was  formed. 

Structurally  the  pulp  is  made  up  of  the  following  elements : 
(a)  Odontoblasts. 
(6)  Connective-tissue  cells. 

(c)  Intercellular  tissue. 

(d)  Bloodvessels. 

(e)  Lymphatics. 
(/)  Nerves. 

The  Odontoblasts  (Fig.  38). — These  are  the  specialized  connective- 
tissue  cells  that  form  the  dentin.  They  lie  along  the  periphery  of 
the  pulp  in  contact  with  the  dentin  walls  and  send  long  protoplasmic 
processes  into  the  dentinal  tubules.  These  processes  have  the  prop- 
erty of  transferring  sensations  of  pain  to  the  nerve  fibrils  within  the 
pulp. 

The  Connective-tissue  Cells. — These  are  stellate  in  form  and  resemble 
the  connective-tissue  cells  in  young,  growing  tissue.  They  are  scattered 
throughout  the  pulp  tissue. 

The  Intercellular  Substance. — This  is  quite  structureless  and  gelat- 
inous in  character.  Scattered  everywhere  through  it  are  the  cells 
just  described. 

The  Bloodvessels  (Plate  II). — These  enter  the  tooth  through  the 
apical  foramen  and  the  larger  vessels  travel  through  the  center  of  the 
pulp,  giving  off  many  branches.  These  break  up  into  capillaries  which 
form  a  rich  network  about  the  periphery  of  the  pulp.  From  these  the 
blood  is  collected  by  veins  that  run  with  the  arteries  and  pass  out 
through  the  foramen.    The  walls  of  the  bloodvessels  in  the  pulp  are 


THE  PULP 


65 


extremely  thin  even  in  the  arteries  and  larger  veins.     This  condition 
renders  the  tissue  particularly  susceptible  to  inflammation. 

The  Lymphatics  (Fig.  39). — llecently  Dr.  Noyes  has  succeeded  in 
demonstrating  that  there  are  lymphatic  vessels  in  the  pulp.  These  are 
connected  through  the  apical  foramen  with  lymphatic  vessels  that 
pass  through  bony  spaces  to  the  mandibular  canal  in  the  lower  jaw 
and  to  the  infra-orbital  canal  in  the  upper  and  then  emerge  from  the 
mental  or  infra-orbital  foramina  and  join  the  lymphatic  vessels  accom- 
panying the  facial  artery  and  vein.  They  empty  into  the  submaxillary 
lymph  nodes.  As  the  lymphatic  capillaries  pass  through  the  apical 
space  after  emerging  from  the  tooth  root  they  are  joined  by  vessels 
that  come  from  the  gums  and  peridental  membrane  so  that  there  is  a 
most  complete  lymphatic  anastomosis  between  the  gums,  the  peri- 
dental membrane  and  the  pulp. 


Fig.  38. — Odontoblasts.  The  section  cuts  obliquely  through  the  odontoblasts. 
F,  fibrils;  A^,  nuclei  of  odontoblasts;  N',  nuclei  of  connective-tissue  cells;  W,  layer  of 
Weil,  not  well  shown.      (About  80  X.)      (Noyes.) 


The  Nerves. — Several  trunks  enter  the  tooth  through  the  apical 
foramen  and  run  through  the  center  of  the  pulp  giving  off  branches. 
These  branches  pass  to  the  periphery  and  form  a  network  at  the 
base  of  the  odontoblasts  and  secondary  arborizations  around  each 
odontoblast.  None  of  the  nerve  fibrils  enter  the  tubules  in  the  dentin. 
Sensation  in  the  dentin  is  due,  therefore,  to  the  irritation  of  the  proto- 
plasmic processes  of  the  odontoblasts  which  transfer  these  irritations 
to  the  nerve  fibers  in  physiological  contact  with  them. 
5 


66 


HISTOLOGY  OF  THE  TEETH 


Function  of  the  Pulp^ 

(a)  The  formation  of  dentin. 

(6)  A  sensory  function.  It  responds  to  heat  and  cold,  and  also 
gives  the  sensation  of  pain  when  irritated. 

Secondary  Dentin. — This  is  dentin  that  is  sometimes  formed  after 
the  normal  amount  of  dentin  has  been  laid  down  and  the  pulp  has 
ceased  to  functionate.  It  is  due  to  irritation  of  the  pulp  by  some 
external  agent  and  this  organ  responds  by  attempting  to  again  perform" 
the  duties  for  which  it  was  designed. 


r- 

' 

v_ 

I  ' 

;  " 

r 

*W     1  •« 

1 

} 

I 

^ 

% 

■  ""ft 

J 

^- 

/    ■ 

^ 

^'^'/ 

i 

'.% 

*i*r 

Fig.  39. — Transverse  section  just  at  the  apex  of  the  root,  showing  injected  lymphatic 
vessels  in  the  peridental  membrane  and  in  the  canals  passing  to  the  pulp  (oc,  2;  obj., 
16  mm. ;  reduced  one-third).     (Noyes.) 


The  Attachment  of  the  Teeth. — As  has  been  previously  stated,  the 
teeth  are  not  to  be  considered  a  part  of  the  osseous  system  of  the 
body,  as  they  bear  no  relation  to  it  from  a  point  of  origin.  Of  what 
system  then  are  they  a  part?  It  has  been  clearly  proved  that  these 
organs  are  appendages  of  the  skin  that  have  through  the  processes 
of  evolution  become  highly  specialized  into  the  form  that  we  see  them 
in  the  various  animals  and  in  man.  The  simplest  form  of  tooth  is 
seen  in  some  of  the  fishes.  It  consists  of  a  cone  of  enamel  covering 
a  calcified  connective-tissue  papilla  containing  tubules  and  closely 
simulating  dentin.  This  in  turn  rests  upon  a  second  mass  of  calcified 
connective  tissue  like  unto  the  cementum.    Into  this  latter  structure 


THE  PERIDENTAL  MEMBRANE  67 

the  fibers  of  the  underlying  tissue  are  built.  To  such  a  simple  form  of 
tooth  no  bone  is  in  any  way  related.  In  the  attempt  to  find  from  what 
structures  the  teeth  were  evolved  it  was  noted  that  the  dermal  scales 
on  the  bodies  of  certain  fish,  i.  e.,  the  shark  and  sturgeon,  were  but 
duplicates  of  the  simple  forms  of  teeth  just  described.  This  fact, 
together  with  other  sufficient  proof,  left  no  question  but  that  the  teeth 
were  really  dermal  appendages  that  had  migrated  into  the  mouth. 

From  this  simple  form  of  tooth  attachment  by  fibrous  tissue  to 
underlying  soft  parts  there  are  numerous  variations  of  form  and 
methods  of  attachment  according  to  the  work  that  the  individual 
requires  of  his  teeth  and  the  amount  of  force  exerted  upon  them  in 
doing  this  work.  So  it  is  noted  that  as  the  food  upon  which  an  animal 
subsists  becomes  harder,  the  attachment  of  the  teeth  becomes  firmer. 
To  combat  the  force  of  displacement,  roots  were  evolved  and  bone 
developed  about  them  until  the  perfected  form  of  support,  as  seen 
in  man,  was  reached. 

At  first  thought  it  might  seem  that  the  strongest  way  in  which  to 
hold  a  tooth  in  place  would  be  to  build  the  bone  immediately  against 
the  root  so  as  to  lock  the  tooth  absolutely  in  position.  If  this  were 
done,  however,  the  slightest  blow  upon  the  crown  of  a  tooth  would 
either  fracture  it  at  the  gingival  margin  or  so  severely  shock  the  pulp 
that  its  life  would  be  forfeited.  Furthermore,  the  transmission  of 
the  force  of  mastication  to  the  bones  of  the  head  under  such  favorable 
conditions  would  be  productive  of  severe  traumatic  shock  to  the  brain. 
Nature  avoids  all  of  this  by  placing  between  the  root  of  the  tooth  and 
the  bone  of  the  alveolar  process  a  fibrous  membrane,  the  function  of 
which  is  to  literally  suspend  the  tooth  in  its  socket.  Thus  it  not  only 
retains  the  tooth  perfectly  but  also  acts  as  a  cushion.  This  membrane 
is  called  the  'peridental  membrane  and  may  be  considered  as  the  most 
important  of  all  the  dental  tissues.  Why?  Because  it  makes  no  dif- 
ference how  perfectly  formed  a  tooth  is  or  how  carefully  its  contour 
be  restored  by  dental  operations  correcting  the  ravages  of  caries,  if 
this  membrane,  that  bears  all  the  stress  during  mastication,  is  not  in 
perfect  health,  that  tooth  will  be  proportionately  useless. 

The  Peridental  Membrane. — Definition. — ^The  peridental  membrane 
may  be  defined  as  that  tissue  which  fills  the  space  between  the  surface 
of  the  root  and  the  bony  wall  of  its  alveolus,  surrounds  the  root  occlu- 
sally,  from  the  border  of  the  alveolus,  and  supports  the  gum.     (Noyes.) 

From  this  definition  it  will  be  noted  that  this  membrane  not  only 
covers  that  portion  of  the  root  that  is  within  the  alveolus  but  also 
that  part  between  the  top  of  the  alveolus  and  the  gingival  line.  Indeed 
this  latter  portion  may  be  considered  as  the  most  important  part  of 
the  membrane,  because  it  is  here  that  the  initial  lesions  which  eventually 
lead  to  the  loss  of  the  tooth,  occur. 

Structurally  the  peridental  membrane  is  made  up  of  the  following 
elements : 

White  fibrous  connective  tissue, 


68  HISTOLOGY  OF  THE  TEETH 

Four  varieties  of  cells : 
Fibroblasts. 
Cementoblasts. 
Osteoblasts. 
Osteoclasts. 
Bloodvessels. 
Lymphatics. 
Nerves. 

Epithelial  structures. 
The  White  Fibrous  Connective  Tissue. — A  careful  study  of  the  distri- 
bution of  this  tissue  is  of  absolute  necessity  if  one  is  to  realize  the 
important  role  that  the  peridental  membrane  plays  in  maintaining 
the  tooth  in  a  functionating  condition. 

The  fibrous  tissues  may  be  divided  into  two  classes  of  fibers:  (a) 
The  principal  and  (6)  the  indifferent.  The  first  group  is  the  one 
concerned  in  the  support  of  the  tooth;  the  other  fibers  simply  fill 
the  spaces  between  the  principal  fibers  and  support  the  bloodvessels, 
lymphatics  and  nerves. 

The  Principal  Fibers. — These  are  built  into  the  cementum  in  the 
form  of  fairly  large  bundles.  Upon  emerging  from  the  cementum 
they  break  up  into  smaller  bundles,  bridge  across  the  interspace  and 
are  again  gathered  together  to  be  built  into  the  bone  of  the  alveolar 
process  or  distributed  to  support  the  gum.  This  is  the  general  arrange- 
ment. The  direction,  however,  that  these  fibers  take  as  they  pass 
from  their  point  of  origin  in  the  cementum  to  their  insertion  in  the 
bone  or  gum  is  modified  in  various  parts  of  the  membrane  and  is  in 
definite  relation  to  the  force  brought  to  bear  upon  the  tooth  as  it  per- 
forms the  work  of  mastication  and  upon  the  pressure  exerted  against 
the  supported  gum  tissue.  This  adaptation  is  the  more  perfect  in 
that  this  arrangement  is  the  result  of  this  force  and  the  force  not 
secondary  to  the  building  of  the  fibers.  This  is  demonstrated  more 
clearly  perhaps  if  it  is  borne  in  mind  that  the  cement-building  cells 
are  constantly  at  work  shifting  the  attachment  of  fibers  whenever 
there  is  a  change  in  the  direction  of  force  exerted  on  the  tooth.  If  the 
tooth  is  changed  in  position,  the  arrangement  of  the  fibers  of  the  mem- 
brane will  be  varied  to  accommodate  any  changes  in  the  force  of 
mastication. 

For  the  purpose  of  studying  the  arrangement  of  the  principal  fibers, 
the  membrane  may  be  divided  into  three  segments :  (a)  The  gingival, 
that  part  between  the  border  of  the  alveolar  process  and  the, gingival 
margin;  (b)  the  alveolar,  that  part  situated  between  the  border  of 
the  process  and  the  apex;  and  (c)  the  apical,  that  portion  in  relation 
to  the  apex  of  the  root  (Fig.  40). 

Arrangement  of  the  Fibers  in  the  Gingival  Portion  (Plate  III). — There 
are  four  sets  of  fibers  in  this  area.  The  first  group  arises  from  the  highest 
point  of  attachment  occlusally  on  the  root,  passes  from  this  at  more  or 
Jess  of  a  right  angle,  then  takes  an  occlusal  curve  and  passes  into  the 


PLATE    III 


''.'  ~l'''V'V 


%lt  v-l. 


Longitudinal  Section  of  Peridental  Mennbrane.     (Noyes.) 

Stained  with  hematoxylin  and  eosin.     Showing  part  of  the  lingual  gingivus  and 
border  of  the  alveolar  process. 


THE  PRINCIPAL  FIBERS 


69 


gum  tissue  to  be  lost  aiiKMig  the  fibers  of  the  conneetive  tissue  that 
supports  the  epithelium  of  the  mucous  membrane. 


Fig.  40. — Diagram  of  the  fibers  of  the  peridental  membrane:  G,  gingivaljportion ; 
AL,  alveolar  portion;  Ap.,  apical  portion.  (From  a  photograph  of  a  section  from 
incisor  of  sheep.)     (Noyes.) 

The  second  group  arises  from  an  area  just  below  the  fibers  of  the 
first  group,  passes  out  from  the  cementum  at  right  angles  and  continues 


70 


HISTOLOGY  OF  THE  TEETH 


for  sufficient  distance  into  the  gum  tissue  to  give  this  perfect  support. 
On  the  Ungual  side  these  fibers  run  a  longer  course  than  on  the  labial 
because  the  lingual  gum  receives  a  greater  shock  in  chewing  than  does 
the  labial.  The  distribution  of  this  group  of  fibers  on  the  approximal 
side  is  of  extreme  importance  (Fig.  41) .  Here  they  pass  across  the  inter- 
vening approximal  space  to  the  adjoining  tooth  and  are  built  into  the 
cementum  of  this  tooth.  Each  tooth  receives  and  gives  off  fibers  on 
the  approximal  side  which  are  built  into  its  cementum.    These,  as  they 


Fig.  41. — Transverse  section  of  the  peridental  membrane  in  the  gingival  portion 
(from  sheep) :  E,  epithelium ;  F,  fibrous  tissue  of  gum ;  B,  point  where  peridental  mem- 
brane fibers  are  lost  in  fibrous  mat  of  the  gum ;  P,  pulp ;  F',  fibers  extending  from  tooth 
to  tooth.     (About  30  X.)     (Noyes.) 


pass  across  the  space,  are  closely  interwoven,  forming  a  basket-work 
structure  that  supports  the  overlying  gum  in  a  most  perfect  manner. 
The  third  grouy.  A  little  more  rootward  to  the  second  group  is  another 
set  of  fibers  that  soon  after  passing  from  their  attachment  in  the 
cementum  are  inclined  apically.  These  form  a  very  strong  bundle 
of  fibers.  On  the  labial  and  lingual  sides  they  pass  to  the  outer  sur- 
face of  the  alveolar  process  and  are  attached  to  the  periosteum  cover- 
ing the  bone  here.  On  the  proximal  side  they  either  pass  to  the 
cementum  of  the  adjoining  tooth  or  are  built  into  the  upper  surface 


THE  CELLS  71 

and  sides  of  tfie  bone  that  intervenes  between  the  teeth.  These  fibers 
resist  any  force  that  tends  to  pull  the  tooth  from  its  socket.  They 
form  what  is  known  as  the  dental  ligament. 

The  fourth  gnnqj  are  arranged  like  a  constrictor  muscle  around  the 
gingival  margin  and  keep  the  gum  tissue  in  close  contact  with  the 
neck  of  the  tooth. 

Arrangement  in  the  Alveolar  Portion  (Fig.  40). — Here  are  found  three 
areas  of  variation  in  direction  of  the  fibers.  First:  The  fibers  coming 
off  from  the  cementum  at  the  level  of  the  top  of  the  alveolar  process 
pass  at  right  angles  across  the  intervening  space  to  be  inserted  into  the 
bony  walls  of  the  process.  This  arrangement  is  continued  down  the 
root  of  the  tooth  nearly  one-third  of  the  distance  to  the  apex.  These 
fibers  arise  from  the  cementum  in  strong  bundles  and  then  break  up 
into  fan-like  forms  as  they  cross  the  space  to  be  inserted  into  the  bone. 
In  transverse  sections  of  the  root  at  this  level  it  is  noted  that  the  fibers 
that  come  off  from  the  angles  of  the  roots  do  not  pass  immediately 
across  the  space  but  are  deflected  to  right  and  left.  These  are  the 
fibers  that  resist  any  force  that  tends  to  rotate  the  tooth  in  its 
socket. 

Second:  As  the  lower  portion  of  the  previously  considered  area  is 
approached  the  fibers,  after  leaving  the  cementum,  begin  to  pass 
occlusally  and  are  inserted  somewhat  higher  up  on  the  wall  of  the 
alveolus.  This  arrangement  is  continued  until  the  apical  end  of  the 
tooth  is  reached.  This  area  is  large  and  the  fibers  are  strong  because 
they  have  to  resist  the  greatest  force  exerted  in  mastication,  i.  e., 
the  thrust  force  as  the  jaws  are  closed.  By  these  fibers  the  tooth 
is  actually  suspended  in  its  alveolus. 

Third:  At  the  lower  portion  of  the  apical  third  of  the  root  the 
fibers  again  begin  to  take  a  more  direct  course  from  the  cementum 
to  the  bone  until  they  are  passing  directly  across,  as  noted  in  the  upper 
third. 

The  Arrangement  in  the  Apical  Portion  (Fig.  40). — Here  the  fibers 
after  passing  from  the  cementum  radiate  in  all  directions  before  being 
inserted  into  the  bone.  In  this  way  the  apical  space  is  filled  with  a 
mass  of  fibrous  tissue. 

The  Cells. — Fibroblasts. — These  are  the  cells  that  have  formed 
the  fibers  and  are  looking  after  their  welfare.  They  are  scattered 
throughout  the  entire  membrane. 

Cementoblasts. — These  are  the  cementum-forming  cells  and  lie  in 
contact  with  this  tissue  between  the  points  of  origin  of  the  fibers. 
As  they  form  the  cementum  some  of  the  cells  surround  themselves 
with  it  and  then  take  the  name  of  cement  cells  or  corpuscles.  They 
also  build  into  the  cementum  the  fibers  of  the  membrane. 

Osteoblasts. — These  are  the  bone-forming  cells  and  have  their  station 
on  the  bony  walls  of  the  alveolus.  They  are  active  in  forming  the  bone 
of  the  alveolar  process  that  is  in  juxtaposition  to  the  roots  of  the 
teeth.    They  too  become  bone  cells  when  they  have  surrounded 


72  HISTOLOGY  OF  THE  TEETH 

themselves  with  this  tissue.  The  attachment  of  the  fibers  of  the 
membrane  into  the  bone  is  performed  by  these  elements. 

Osteoclasts. — These  are  the  cells  that  eat  away  the  bone  or  cemen- 
tum  when  there  is  a  demand  for  this  process.  Through  their  action 
the  fibers  of  the  membrane  are  detached  at  any  given  area.  This 
occurs  during  the  absorption  of  the  roots  of  the  deciduous  teeth  and 
it  is  these  cells  that  are  responsible  for  this  process.  They  are  also 
used  when  nature  believes  that  the  bone  in  any  given  place  is  too 
thick  and  heavy  for  the  strain  brought  to  bear  upon  it.  If  so,  these 
cells  are  brought  into  activity  and  destroy  the  thick  bone  by  forming 
marrow  spaces  within  it.  This  occurs  in  the  formation  of  the  alveolar 
process  and  accounts  for  its  cancellous  or  spongy  character. 

Bloodvessels  (Plate  II), — The  peridental  membrane  has  a  very  rich 
supply  of  blood.  The  arteries  enter  the  apical  space  from  the  bone 
beneath.  They  then  give  off  branches  which  pass  into  the  pulp  cavity 
to  supply  the  organ  therein.  The  main  branches  pass  occlusally  in  all 
directions  through  the  peridental  membrane.  They  lie  nearer  the  wall 
of  the  alveolus  than  the  cementum.  As  they  pass  upward  they  receive 
from  and  give  off  branches  to  the  bone  of  the  alveolar  walk  They 
end  by  anastomosing  with  the  bloodvessels  of  the  gum  tissue  and 
help  supply  this  area.  From  this  it  is  noted  that  the  blood  supply 
of  the  gums  and  peridental  membrane  is  intimately  related  so  that 
stimulation  of  gum  tissue  by  massage  and  brushing  will  in  turn  stimu- 
late the  peridental  membrane — a  fact  that  is  of  the  greatest  impor- 
tance in  the  treatment  of  lesions  of  this  latter  structure. 

Lymphatics  (Fig.  42). — It  has  been  shown  that  the  peridental  mem- 
brane is  well  supplied  with  lymphatic  vessels  which  ramify  through  the 
membrane  very  much  as  do  the  bloodvessels.  Small  lymphatic  capil- 
laries also  run  from  the  gum  margin  and  anastomose  with  the  vessels 
in  the  peridental  membrane.  In  the  region  of  the  root  apex  the  lymph 
channels  of  the  peridental  membrane  are  joined  with  those  from  the 
pulp  and  these  larger  vessels  pass  through  the  bone  spaces  to  the  main 
trunks  in  the  mandibular  or  infra-orbital  canals  as  described  under  the 
lymphatics  of  the  pulp. 

The  Nerves, — These  have  the  same  point  of  entrance  and  the  same 
distribution  as  the  bloodvessels  that  have  just  been  described.  It  is 
important  to  note  that  these  nerves  give  to  the  peridental  membrane 
the  sense  of  touch.  This  sense  is  well  developed,  for  the  lightest  con- 
tact is  immediately  recognized. 

Epithelial  Elements. — As  the  function  of  these  structures  is  still  a 
mystery  it  is  sufficient  in  this  text  to  note  that  such  tissues  are  present 
but  that  their  real  significance  still  remains  unknown. 

The  function  of  the  peridental  membrane. 

(a)  A  physical  function,  i.  e.,  the  maintaining  of  the  tooth  in  the 
socket, 

(6)  A  vital  function,  manifested  through  the  agency  of  its  cells  in 
the  formation  of  cementum  and  bone. 


CHANGES  IN  THE  MEMBRANE   WITH  AGE 


73 


(c)  A  sensory  functicju  in  that  it  supplies  the  sense  of  touch  to  the 
tooth. 

Changes  in  the  Membrane  with  Age. — When  the  tooth  first  erupts 
the  space  between  the  root  and  wall  of  the  alveolus  is  relatively  wide. 
Each  year  finds  this  becoming  smaller  and  smaller  because  of  the 
formation  of  new  lamellae  of  cementum  on  the  one  side  and  of  bone 
on  the  other.     The  peridental  membrane  grows  proportionately  thinner 


Fig.  42. — Unstained  section,  showing  lymph  capillaries  of  the  tooth  side  of  the 
gingivae  and  their  drainage  through  the  ligamentum  circulare  to  the  peridental  mem- 
brane.    (Noyes.) 


as  it  is  thus  encroached  upon.  However,  there  is  always  a  membrane 
present  no  matter  what  the  age  of  the  individual  may  be.  In  other 
words,  the  bone  and  cementum  never  come  in  immediate  contact  with 
each  other.  This  thinning  of  the  membrane  makes  it  less  resistant 
to  irritations  and  so  predisposes  inflammatory  conditions.  Hence 
diseases  of  the  peridental  membrane  are  more  frequently  found  after 
adolescence. 


74  HISTOLOGY  OF  THE  TEETH 

The  Alveolar  Process. — As  has  been  previously  emphasized,  the  bone 
of  this  process  is  built  secondary  to  the  formation  of  the  teeth  or  rather 
coincident  to  their  eruption.  It  is  a  product  of  function  and  is 
arranged  as  to  its  structure  in  a  way  that  will  best  resist  the  forces 
that  are  brought  to  bear  upon  it.  In  the  upper  jaw  we  find  a  dense, 
hard  layer  of  bone  about  the  necks  of  the  teeth  labially  and  buccally. 
In  the  incisor  and  cuspid  region  where  much  force  is  exerted  upon  the 
whole  length  of  the  roots  the  bone  is  quite  thickened  over  their  entire 
labial  surfaces.  This  is  well  demonstrated  in  those  lower  animals  that 
use  these  teeth  for  seizing  and  tearing  their  prey.  Over  the  buccal 
roots  of  the  bicuspids  and  molars  it  is  very  thin.  Lingually,  all  the 
teeth  of  the  upper  arch  are  well  supported. 

In  the  lower  arch  again  is  found  the  compact  bone  about  the  necks 
of  the  teeth  and  their  roots  well  supported  buccally,  as  most  of  the 
strain  is  in  this  direction. 

The  great  mass  of  bone  of  both  the  maxilla  and  the  mandible  is 
made  up  of  the  cancellated  variety  about  the  periphery  of  which  is  a 
layer  of  thick,  dense  bone.  The  wall  of  each  alveolus  joins  this  thick- 
ened layer  at  its  upper  border.  Below  this  point  of  union  the  wall 
of  the  alveolus  is  surrounded  with  cancellated  bone  so  that  the  alveolar 
process  as  a  whole  is  quite  elastic  and  springy.  In  connection  with 
our  reference  to  bony  tissue  it  is  well  to  mention  the  fact  that  this  is 
living  tissue,  a  specialization  of  the  connective  tissues,  adapted  for 
perfect  support  and  that  it  is  ever  throughout  life  undergoing  constant 
change  as  a  result  of  the  mechanical  forces  brought  to  bear  upon  it. 
By  virtue  of  the  ability  to  make  such  changes,  nature  is  able  to  meet 
any  requirement  that  is  demanded,  even  though  it  be  far  different  from 
the  original  condition  for  which  the  bone  was  built.  So  in  examining 
a  specimen  of  bony  tissue  under  the  microscope  various  forms  of  bone 
cell  activity  are  seen  going  on,  representing  different  stages  of  bone 
formation  and  absorption. 

The  Gums. — The  soft  tissue  overlying  the  alveolar  processes  is 
known  as  the  gums.  It  is  composed  of  mucous  membrane  under 
which  is  a  submucous  tissue  which  lies  on  and  is  firmly  attached  to  the 
periosteum  of  the  bony  process.  The  cells  of  the  epithelial  layer  of  the 
mucous  membrane  are  cornified. 

The  gum  tissue  about  the  necks  of  the  teeth  is  supported  and  held 
in  position  by  fibers  from  the  peridental  membrane  which  pass  from 
the  cementum  into  the  submucosa.  The  bloodvessels  and  lymphatics 
of  the  gums  anastomose  freely  with  those  of  the  peridental  membrane. 
vStimulation  of  the  circulation  in  the  gum  tissues  therefore  also  causes 
a  free  flow  of  blood  through  the  peridental  membrane  a  factor  of  much 
importance  in  maintaining  the  health  of  this  membrane.  On  the  other 
hand  this  free  anastomosis  gives  excellent  opportunity  for  infection 
of  the  peridental  membrane  from  gum  lesions  or  even  for  systemic 
infection. 


TOOTH  FORMATION 


75 


Tooth  Formation. — The  first  sign  of  the  formation  of  teeth  is  seen 
in  the  embryo  at  about  two  and  a  half  months.  Ahjng  the  top  of  each 
arch  (upper  and  h>wer)  there  is  seen  a  heaping  up  of  the  cells  of  the 
outer  layer  of  tissue.  If  a  cross-section  is  made  of  the  arch,  it  will  be 
noted  that  these  cells  are  also  dipping  down  into  the  underlying  tissue. 
This  formation  is  known  as  the  dental  ridge.  From  the  lingual  side 
of  this  ridge  a  shelf -like  growth  is  formed  called  the  lamina  (Fig.  43). 
At  intervals  along  the  lamina,  corresponding  to  the  location  of  each 
tooth,  little  buds  grow  from  it.  The  under  surface  of  these  buds 
becomes  indented,  taking  on  the  appearance  of  an  inverted  cup.  This 
cup-like  structure  is  now  known  as  the  ena^nel  organ  (Fig.  44),  and 
will  soon  begin  to  lay  down  enamel  along  its  inner  surface.     The  cells 


Fig.  43. — The  dental  ridge  and  dental  lamina 


lining  this  surface  are  the  enamel  cells  or  ameloblasts  and  are  active 
in  the  formation  of  this  substance.  The  enamel  organ  is  of  epithelial 
tissue  origin. 

As  the  enamel  organ  is  forming,  the  cells  of  the  tissue  into  which  it 
grows  begin  to  take  on  activities.  As  fast  as  the  infolding  of  the 
base  of  the  enamel  organ  takes  place  the  indentation  is  filled  in  with 
these  active  underlying  tissues  until  a  papilla  is  formed.  This  is  known 
as  the  dental  'papilla  (Fig.  44) .  This  structure  is  of  connective-tissue 
origin  and  will  become  active  in  the  formation  of  the  dentin.  Growth 
of  the  papilla  continues  until  it  has  assumed  the  shape  of  the  crown  of 
the  tooth  to  be  formed.  To  this  structure  formed  by  the  enamel  organ 
and  dental  papilla  is  given  the  name  of  tooth  germ. 


76 


HISTOLOGY  OF  THE  TEETH 


After  the  dental  papilla  has  been  formed,  the  cells  at  its  base  develop 
fibrous  tissue  which  grows  up  and  around  the  outer  side  of  the  enamel 
organ  and  over  its  top  so  that  the  tooth  germ  is  enclosed  in  a  fibrous 
sac.  This  combination  of  structures,  i.  e.,  the  fibrous  wall,  the  papilla 
and  the  enamel  organ  constitutes  the  dental  follicle.  This  is  completed 
by  the  end  of  the  twelfth  week. 


Fig.  44. — The  enamel  organ.     The  outer  tunic  connected  to  the  lamina  by  the  cord;  the 
dental  papilla  growing  up  into  the  cap.     The  spaces  are  shrinkage  spaces.    (Noyes.) 


Just  before  the  enclosure  takes  place  a  secondary  bud  is  given  off 
from  the  enamel  organ,  usually  near  its  point  of  origin  from  the  lamina, 
which  grows  downward  to  become  the  enamel  organ  of  the  permanent 
tooth  (Fig.  45). 

Soon  after  the  formation  of  the  dental  follicle  the  bone  of  the  jaw 
below  this  structure  sends  up  processes  which  pass  to  the  lingual  and 
labial  side  of  the  follicle.  Later  bony  growth  appears  on  the  proximal 
sides  and  finally  the  top  is  covered  over.  This  bony  structure  is  what 
is  known  as  the  dental  crypt  and  simply  serves  as  a  protection  to  the 
forming  tooth.    The  dental  crypt  persists  until  the  entire  crown  is 


TOOTH  FORMATION 


77 


developed  and  the  tooth  ready  to  erupt  when  the  top  is  absorbed 
and  the  tooth  passes  into  the  mouth. 

At  about  the  sixteenth  week  the  dentin  and  the  enamel  begin  to 
form,  the  former  on  the  outer  edge  of  the  dental  papilla  and  the  latter 
on  top  of  this  dentin. 


Fig.  45. — The  tooth  germ  showing  the  bud  for  the  permanent  tooth  at  P.  Calci- 
fication is  just  beginning;  /?',  follicle  wall;  D,  dental  papilla;  T,  inner  tunic;  T',  outer 
tunic;  S,  stellate  reticulum;  O,  odontoblasts;  A,  ameloblasts;  B,  bone.     (Noyes.) 


The  roots  of  the  teeth  do  not  appear  until  the  tooth  begins  to  take 
on  the  process  of  eruption.  At  this  time  also  the  first  of  the  cemen- 
tum  is  seen.  This  is  formed  by  cells  in  that  fibrous  tissue  that  grew 
up  and  around  the  enamel  organ  to  complete  the  follicle.  This  fibrous 
tissue  now  may  be  considered  as  the  peridental  membrane.  Coinci- 
dent with  the  formation  of  cementum  by  the  cells  on  the  inner  side 


78  HISTOLOGY  OF  THE   TEETH 

of  this  membrane  there  is  a  deposit  of  bone  laid  down  by  the  osteo- 
blasts on  the  other  side  of  the  membrane.  This  is  the  beginning  of 
the  alveolar  process. 

The  first  permanent  molars  are  the  only  permanent  teeth  for  which 
the  enamel  organ  arises  directly  from  the  lamina.  The  enamel  organs 
for  the  second  and  third  permanent  molars  arise  from  the  buds,  of 
the  first  and  second  permanent  molars  respectively. 


Fig.  46. — Front  view  of  skull.     Note  the  relation  of  the  permanent  incisors  and  cuspids 
to  each  other  and  the  roots  of  the  temporary  teeth.     (Noyes.) 

THE  DEVELOPMENT  OF  THE  JAWS. 

While  it  is  impossible  in  the  space  alloted  this  subject  to  go  into 
detail  regarding  the  growth  of  the  jaws,  yet  it  is  quite  necessary 
that  the  dental  hygienist  should  know  briefiy  the  plan  upon  which 
nature  builds  under  normal  conditions.    For  an  exhaustive  study 


THE  DEVELOPMENT  OF  THE  JAWS  79 

of  this  subject  the  student  is  referred  to  Dr.   Noyes's  text-book, 
Dental  Histology  and  Embryology. 

In  a  comparison  of  the  skull  of  an  infant  at  birth  with  that  of  an 
adult  it  is  noted  that  as  growth  proceeds  there  is  practically  twice 
as  much  development  below  the  nasal  spine  of  the  frontal  bone  as 
above  it.  This  great  downward  growth  takes  place  mostly  in  the 
region  of  the  mouth  and  is  due  primarily  to  the  formation  and  sub- 
sequent eruption  of  the  teeth,  and  secondarily  to  a  continued  growth 
of  bone  thrown  out  to  act  as  a  supporting  structure  for  these  organs 
(Fig.  46) .  This  downward  growth  begins  with  the  eruption  of  the  de- 
ciduous denture  and  continues  until  all  the  permanent  teeth  anterior  to 
the  first  molars  are  in  position.  After  the  completion  of  the  deciduous 
denture  two  new  directions  of  growth  manifest  themselves,  a  lateral 
or  expanding  growth  to  allow  for  the  difference  in  size  between  the 
teeth  of  the  deciduous  and  permanent  dentures,  and  a  forward  one 
to  make  room  for  the  developing  permanent  molars.  Hence  we  note 
that  the  growth  and  development  of  the  jaws  takes  place  in  three 
directions,  i.  e.,  a  vertical  growth,  which  is  downward  in  the  upper 
jaw  and  upward  in  the  lower  and  is  coincident  with  tooth  eruption; 
a  lateral  growth;  a  forward  growth.  This  development  continues  until 
all  the  teeth  are  in  position  and  occlusion  is  established. 


CHAPTER  III. 
THE  TEETH  AS  A  MASTICATING  MACHINE. 

By  CHARLES  R.  TURNER,  M.D.,  D.D.S. 

An  analysis  of  the  reasons  for  preserving  the  teeth  gives  first  impor- 
tance to  their  preservation  that  they  may  perform  their  fmictions  as 
a  part  of  the  human  organism,  and  play  their  part  in  that  sum  total 
of  activities  which  go  to  make  up  the  physical  life  of  the  human 
animal.  As  so  much  attention  is  now  being  given  to  the  matter  of 
tooth  conservation  it  is  proper  to  be  informed  as  to  the  important 
part  taken  by  the  teeth  in  one  of  the  most  essential  of  the  distinctive 
animal  functions,  indeed,  one  which  is  necessary  to  the  preservation 
of  life  itself.  Furthermore,  it  is  one  of  the  dictums  of  physiology 
that  any  part  of  the  body  which  ceases  to  perform  its  functions  atro- 
phies, or  the  character  of  its  tissues  degenerates,  and  in  course  of 
time  is  incapable  of  performing  its  function;  and  so  the  duties  of  the 
teeth  have  a  twofold  interest  for  us. 

In  order  then  to  present  the  case  for  the  preservation  of  the  teeth,  as 
it  were,  something  must  be  said  about  their  functions  in  the  human 
body,  and  in  that  connection  as  a  machine,  or  as  a  part  of  a  machine, 
concerned  in  the  preparation  of  the  food  for  subsequent  stages  in  the 
digestive  process. 

To  appreciate  fully  the  part  taken  by  the  teeth  in  the  activities  of 
the  human  organism,  it  might  be  interesting,  and  it  will  certainly 
give  a  good  background  for  the  study  of  the  human  dental  mechan- 
ism, to  take  some  account  of  the  way  the  teeth  have  developed  to 
perform  their  present  functions. 

The  basal  functions  of  animal  as  distinguished  from  plant  life,  and 
as  fundamental  to  existence  itself,  are: 

1.  Alimentation. 

2.  Respiration  and  circulation. 

3.  Locomotion. 

4.  Reproduction. 

Evolution  of  Tooth  Forms. — ^In  the  simplest  form  of  animal  life,  as 
for  example  in  a  unicellular  body,  the  ameba,  we  have  the  process  of 
alimentation,  or  the  securing  of  nutrition,  an  extremely  simple  one. 
The  animal  is  afloat  in  the  water  and  extracts  its  nutriment  there- 
from, the  nutritive  elements  are  absorbed  through  the  cell  wall  and 
nutrition  is  effected  through  a  simple  process  of  osmosis. 

No  one  fact  so  impresses  the  student  of  zoology  as  the  relation- 


EVOLUTION  OF  TOOTH  FORMS  81 

ship  between  the  form  and  structure  of  the  various  parts  of  an  animal 
organism  and  the  functions  they  are  called  upon  to  perform.  It  is 
very  interesting  to  note  the  adaptive  moflification  of  the  structures 
to  changes  in  these  bodily  functions,  and  to  observe  how  they  have 
been  modified  during  the  various  stages  in  the  development  from 
the  lowest  organisms  up  to  the  highest  forms. 

As  the  scale  of  animal  life  is  ascended  and  a  multiplication  of  func- 
tions occurs,  differentiations  of  tissue  appearing  here  and  there  are 
found,  which  occur  as  a  result  of  a  certain  function  falling  upon  that 
tissue.  Certain  cells  are  given  over  to  the  function  of  reproduction; 
certain  other  cells  or  collections  of  cells  are  specialized  for  locomotion, 
etc. 

In  some  of  the  lower  forms  of  animals,  before  the  vertebrates,  there 
is  a  simple  tube  like  a  channel  devoted  to  alimentation;  the  food  goes 
in  one  end  and  the  excreta  are  ejected  at  the  other.  There  is  no 
special  collection  of  cells  at  the  beginning  of  this  tube  to  prepare  the 
food.  In  the  ccBlenterata,  for  example,  the  alimentary  canal  is  not 
separate  from  the  general  body  cavity,  but  in  the  annuloida  and 
annulosa  it  is  a  distinct  tube. 

A  little  higher  in  the  scale,  as  in  some  of  the  insects,  the  crabs  and 
the  crustaceans,  there  are,  at  the  beginning  of  this  alimentary  tract, 
cells  which  are  concerned  to  some  extent  with  the  preparation  of  the 
food  for  its  passage  through  the  canal.  There  is  no  real  masticating 
apparatus,  however,  even  in  many  of  the  lowest  of  the  vertebrate 
animals,  but  the  first  thing  that  at  all  appears  like  it  occurs  in  some 
of  the  lower  fishes,  in  the  hag-fishes  and  in  the  lamprey  eels.  The 
latter  have  a  suctorial  mouth  which  they  attach  to  some  object, 
either  the  side  of  a  larger  fish  or  a  stone  covered  with  moss,  and 
obtain  their  nutrition  from  it  by  a  process  of  suction.  Inside  of  this 
mouth  are  layers  of  cells  which  are  rather  horn-like  in  character. 
They  are  for  the  purpose  of  imbedding  themselves  in  the  substance  to 
which  the  mouth  is  applied  and  of  affording  a  firm  hold  so  that  the 
animal  may  draw  its  sustenance.  This  is  perhaps  the  very  simplest 
type  of  differentiation  of  tissue  for  this  purpose. 

In  the  vertebrate  animals  the  cells  constituting  the  tissues  at  the 
entrance  of  the  alimentary  canal  are  specialized  with  a  view  to  assist 
ing  in  the  process  of  either  securing  or  preparing  the  animal's  food. 
The  apparatus  is  simple  in  the  less  highly  developed  orders  and 
becomes  a  more  complicated  instrument  as  the  scale  is  ascended. 
The  food  convenient  to  the  animal  or  required  by  it,  and  the  food- 
reducing  mechanism  are  in  constant  correspondence.  Out  of  this 
necessity  has  developed  teeth.  The  teeth  have  developed  in  accord 
with  and  to  meet  the  needs  of  the  food  which  the  animal  utilizes. 
They  are  corneal  or  horn-like  in  some  of  the  lower  orders  and  as  we 
go  upward  they  become  calcified.  They  are  simple  cones  or  they 
are  modified  under  certain  conditions  to  forms  which  serve  better 
their  functions. 


82  THE  TEETH  AS  A  MASTICATING  MACHINE 

Fishes  are  the  lowest  vertebrate  type  that  have  calcified  teeth; 
they  are  simply  calcified  cones  arranged  around  the  border  of  the 
jaws  and  serve  to  hold  the  food.  Some  of  the  teeth  are  recm-ved 
and  serve  like  the  barb  of  a  fish-hook  to  prevent  the  escape  of  the 

prey  (Fig.  47). 


A 

j^-^I-^^^M 

W^^'      '                   .X..MUH^» 

3 

wmm^Mmmm^  -4 

-4as^ — ' 

Fig.  47. — Teeth  of  the  python,  bull-frog,  horned  toad  and  water  snake. 

Of  the  amphibians  some  have  no  teeth,  as  the  toad,  while  others, 
such  as  the  frog,  have  teeth  not  unlike  those  of  fish,  at  least  always 
in  the  upper  jaw  for  the  bullfrog  has  no  lower  teeth. 

Of  the  reptiles  many  have  teeth.  The  lizards  eat  butterflies,  worms, 
insect  larvae,  etc.,  while  snakes  live  on  amphibians  and  their  larvae 
and  fish,  and  the  mperine  snakes  on  small  mammals.  Crocodiles  and 
turtles  eat  fish,  small  amphibians  and  insects.  The  snakes  do  not 
chew  their  prey  but  swallow  it  whole.  The  lower  jaw  is  jointed  in 
the  center  and  articulates  with  the  skull  through  the  quadrate  bone, 
thus  allowing  the  mouth  to  open  very  wide,  but  the  teeth  serve  only 
for  seizing  and  holding  the  prey.  In  the  venomous  snakes  in  the 
upper  jaw  are  found  the  "poison  fangs"  which  have  a  channel  leading 
to  the  poison  sac.  The  chelonidce  or  turtles  have  a  horn-like  covering 
for  the  border  of  the  jaw. 

The  birds,  of  course,  have  no  teeth,  the  beak  being  a  horny  sheath- 
ing of  the  ends  of  the  jaw  bones.  In  some  the  edge  is  serrated.  In 
no  other  class  is  found  a  greater  variation  in  the  food-preparing  appa- 
ratus, or  greater  adaptation  to  the  food  supply.  The  beak  serves 
largely  to  obtain  the  food.  In  the  grain-eating  birds  the  gizzard  per- 
forms mastication.  Ducks  have  soft-edged  beaks  for  sifting  the  food 
out  of  the  mud.  The  skulls  of  the  hawk,  heron,  English  sparrow, 
crow  and  toucan  shown  give  an  idea  of  this  variation.  The  crow  sub- 
sists largely  on  grain,  and  very  often  takes  grain  such  as  corn  out 
of  the  husk.  It  has  rather  a  strong  beak  suited  for  this  purpose 
(Fig.  48). 

The  skull  of  the  blue  heron  is  also  shown.  These  are  aquatic  birds 
and  their  food  comes  from  the  bottom  of  the  water,  or  in  fact,  down 
in  the  mud  w^here  they  go  after  little  frogs  and  little  fish,  and  various 


EVOLUTION  OF  TOOTH  FORMS 


S3 


other  inhabitants  of  the  water.  Also  is  shown  jjasser  domestwus  or 
English  sparnnv,  which  subsists  on  very  much  the  same  type  of  food 
as  the  crow,  only  it  is  a  little  more  omnivorous,  and  the  beak  is  very 
much  the  same.  We  also  have  the  skull  of  a  South  American  bird, 
the  toucan,  which  is  a  fruit-eating  bird.     The  serrations  on  the  beak. 


E 

i 

P^T^^> 

1 

■"^ 

1 

^Hm^-^  _^^^^^^^^^^^^^^^^^^^^H 

Fig.  48. — Beaks  of  birds,  showing  functional  modifications. 

which  are  useful  in  cutting  through  the  skin  of  fruit  and  in  sifting  out 
the  stones,  will  be  noted  as  a  rather  interesting  adaptation  to  the 
needs  of  this  bird.  Lastly,  we  see  the  skull  of  the  licnck,  one  of  the 
carnivorous  birds.     The  beak  of  the  hawk  is  verv  strong,  and  is  used 


Fig.  49. — Skulls  of  three  turtles. 


for  the  purpose  of  killing  the  prey;  smaller  birds  and  mammals,  in 
the  case  of  large  hawks,  and  insects  and  food  of  that  sort  in  case  of 
smaller  hawks. 

There  is  very  much  the  same  type  of  masticating  apparatus,  if  it 
may  be  so  called,  in  the  turtle.    Fig.  49  shows  the  skull  of  a  large 


84  THE  TEETH  AS  A  MASTICATING  MACHINE 

green  turtle,  the  hawk-bill  turtle  and  the  snapping  turtle,  the  beaks  of 
the  last  two  mentioned  covered  with  a  very  hard,  dense  membrane, 
which  is  very  horn-Uke  in  quahty,  and  is  very  much  hke  the  beak 
of  birds,  the  purpose  of  it  being  purely  to  crush  the  food,  and  to 
cut  off  a  definitely  sized  amount  of  food  in  order  that  it  may  be  swal- 
lowed. Of  course  it  is  not  possible  for  this  animal  to  chew  its  food. 
The  first  type  of  tooth  that  is  of  very  great  interest  other  than 
merely  as  a  fang,  or  something  of  that  sort,  is  the  molar  of  the  ungu- 
lates which  are  herbivorous  and  granivorous  animals  (Fig.  50).  Her- 
bivorous animals  live  on  grain  and  on  vegetable  fiber,  both  of  which 
require  considerable  trituration  in  order  to  be  successfully  acted  upon 
by  the  digestive  juices,  solvents  and  ferments  farther  down  in  the 
digestive  tract.  For  example,  corn  and  other  grains  will  pass  down 
the  alimentary  tract  of  any  of  these  animals,  entirely  untouched 
unless  the  outer  membrane  is  broken,  therefore  in  order  to  be  success- 
fully digested  they  have  to  be  well  triturated. 


Fig.  50. — Skull  of  a  sheep. 

The  series  of  molar  teeth  of  the  horse  is  a  real  grinding  machine. 
The  surface  is  raised  into  elevations  alternating  with  depressions. 
The  elevations  are  the  enamel,  the  depressions  between,  the  cemen- 
tum.  The  cementum  is  very  much  softer,  and  as  the  tooth  wears 
down  the  enamel  which  is  harder  and  more  resistant  than  the  cemen- 
tum wears  much  less  rapidly,  so  that  the  surface  is  continually  kept 
rough  for  grinding  purposes. 

This  animal  has  a  great  latitude  in  the  side-to-side  movement  of 
the  jaw;  or,  to  speak  more  technically,  the  lateral  excursion  of  the 
mandible  of  herbivorous  animals  is  very  marked.  The  jaw  does  not 
move  much  backward  and  forward;  in  fact,  it  hardly  moves  in  these 
directions  at  all,  but  it  moves  from  side  to  side.    The  result  is  that 


EVOLUTION  OF  TOOTH  FORMS 


85 


these  serrations  run  IVoni  I'rojit  to  hack.  This  is  exactly  tiie  reverse 
of  the  form  of  the  molars  found  in  the  rodents,  in  which  a  backward- 
and-forward  movement  of  the  mandible  is  responsible  for  the  grind- 
ing, necessitating  a  different  arrangement  of  the  occlusal  surface  of 
the  teeth. 

John  Ryder,  many  years  ago,  pointed  out  the  fact  that  from  an 
examination  of  the  surfaces  of  the  molar  teeth  of  any  animal,  extinct 
or  living,  he  could  without  reference  to  the  skull  indicate  the  way  in 
which  the  mandible  was  accustomed  to  move. 


Fig.  51. — Carnivorous  and  herbivorous  skulls. 


The  front  of  the  mouth  of  the  horse  is  provided  with  incisor  teeth 
which  bite  and  pinch  off  the  grass  and  other  foods  which  the  animal 
secures.  The  canine  is  quite  rudimentary,  and  usually  absent  in 
the  mare. 

Cows  have  incisors  only  in  the  lower  jaw,  and  the  biting  is  done 
between  the  upper  lip  and  the  lower  teeth. 

Now  passing  over  one  or  two  important  orders  as  not  being  espe- 
cially interesting,  next  comes  a  very  large  family  in  the  animal  king- 
dom, the  carnivorous  animals,  which  differ  from  the  class  just  described 
in  the  character  of  their  teeth  and  also  in  the  manner  of  the  move- 
ment of  the  mandible.  In  studying  these  dentures  three  funda- 
mental elements  and  their    relationship  must  be  constantly  borne 


S6  THE  TEETH  AS  A  MASTICATING  MACHINE 

in  mind;  the  food  supply,  the  teeth  and  the  manner  in  which  the 
mandible  is  capable  of  moving. 

For  a  comparison  of  dentures  the  skulls  of  a  large  western  cat  and 
of  an  ordinary  buck  sheep  are  pictured  together  (Fig.  51).  A  vast 
difference  in  the  grinding  teeth,  as  shown  in  their  respective  mandibles, 
is  noted.  In  one  the  teeth  are  narrow,  in  the  other  the  teeth  are  wide. 
Viewed  from  the  side  it  is  seen  that  the  carnivorous  molars  have 
sharp  edges  and  are  rather  more  like  knives  than  the  grinders  of  the 
herbivorous  series.     In  one  there  are  very  pronounced  canines. 

There  is  a  very  marked  difference  in  the  temporomandibular  articu- 
lation of  these  two  animals.  In  the  case  of  the  herbivorous  animals 
there  are  broad,  flat  glenoid  fossae  to  render  possible  the  large  range 
of  lateral  excursion  of  the  mandible.  On  the  other  hand,  the  car- 
nivorous animals  have  no  lateral  excursion.     The  condyles  fit  into 


Fig.  52.— Skull  of  a  tiger. 

the  fossae  so  tightly  as  to  make  almost  a  hinge  joint;  and  in  some 
instances  the  distal  part  of  the  eminentia  articularis  so  far  overhangs 
its  glenoid  fossa  that  it  cannot  be  seen.  It  is  only  with  great  difficulty 
that  the  condyles  can  be  gotten  out  of  these  fossae;  indeed  in  some 
instances  they  cannot  be  gotten  out  without  breaking  the  skull. 

In  the  skull  of  an  Indian  tiger,  it  may  be  noticed  that  the  molar 
teeth  are  of  the  type  described  (Fig.  52).  They  are  very  sharp  and 
there  are  tubercles  on  each  side  just  before  the  cingulum  is  reached, 
and  in  the  closure  of  the  mouth  the  teeth  pass  by  each  other  very 
much  like  the  blades  of  a  pair  of  shears.  Besides  the  articulation  of 
the  mandible  which  serves  to  keep  it  in  line,  the  upper  canines  fit  into 
the  spaces  back  of  the  lower  canines  and,  locking  the  occlusion  like 
guide-pins,  prevent  lateral  movement. 

The  carnivora  have  greater  crushing  power  in  their  jaws  in  com- 
parison to  their  size  than  any  other  animals.    This  is  partly  due  to 


SOLUTION  OF  TOOTH  F0Ri\4S 


S7 


the  tremendous  temporal  muscles  which  are  attached  to  the  Ijroad 
temporal  ridges. 


Fig.  53. — Skull  of  a  black  bear. 


In  the  skull  of  a  black  bear  is  observed  almost  the  same  type  of 
dentition  as  that  of  the  cats,  only  the  canine  teeth  are  a  little  less 
powerful,  and  the  carnassial  teeth  at  the  rear  are  not  so  strongly 
marked  (Fig.  53). 


Fig.  54. — Skull  of  a  coyote. 


A  typical  carnivorous  dentition  is  found  in  the  canidoB  or  dog  family 
and  in  a  skull  of  the  canis  latrans  illustrated  are  shown  the  several 


88  THE  TEETH  AS  A  MASTICATING  MACHINE 

types  of  teeth  definitely  marked;  the  incisors,  three  on  each  side,  the 
canines,  the  premolars  and  the  molars  (Fig.  54).  In  the  upper  jaw 
there  are  four  premolars  and  two  molars,  whereas  in  the  lower  jaw 
there  are  three  molars  and  four  premolars.  The  fourth  upper  pre- 
molar and  the  first  lower  molar  are  known  as  the  carnassial  teeth  and 
they  are  the  chief  cutting  teeth  of  these  animals. 

In  the  wolf  and  the  American  fox  the  dentition  is  precisely  the 
same.  In  some  of  the  smaller  carnivorous  animals,  the  badger,  the 
otter  and  the  raccoon,  the  dentition  is  very  much  the  same. 

The  next  family  is  the  rodents,  who  have  a  highly  developed  type 
of  incisor.  Thus  far  attention  has  been  given  chiefly  to  the  molar 
teeth.  In  the  rodents  the  incisor  teeth  are  of  the  greater  importance. 
In  the  skull  of  the  beaver  the  upper  incisor  tooth  has  a  chisel-like 
beveled  edge  (Fig.  55).     It  has  enamel  only  upon  its  labial  surface. 


Fig.  55. — Skulls  of  rodents. 

which  is  supported  by  the  dentin.  There  is  no  enamel  on  the  back 
of  the  tooth.  As  the  dentin  wears  away  the  enamel  is  left  standing 
and  chips  away  and  thus  always  preserves  a  sharp  edge.  It  is  really 
a  self-sharpening  tool.  It  has  a  persistent  pulp  and  grows  out  as  it  is 
worn  off. 

The  rodents  have  practically  no  lateral  motion  to  the  mandible, 
but  great  backward-and-forward  movement.  Their  molars  are 
ridged,  but  the  ridges  run  transversely,  so  that  in  the  backward-and- 
forward  movement  of  the  mandible  they  can  do  the  same  kind  of 
grinding  as  the  herbivorous  animals  do  in  the  lateral  movement 
(Fig.  56). 

Approaching  nearer  to  man  in  the  scale  of  animal  life,  as  for  example 
in  the  apes,  dentures  are  found  which  are  approximately  like  the 
human  one.  Thus  in  the  new  world  monkeys  (Fig.  57)  almost  exactly 
the  same  type  of  denture  is  observed  as  that  of  man,  except  that 


EVOLUTION  OF  TOOTH  FORMS 


89 


there  are  three  premolars  instead  of  t\v(j.     Tliere  are  two  incisors, 
a  canine,  three  premolars  and  three  molars  on  each  side. 


Fig.  56. — Skulls  of  rodents,  showing  transverse  ridges  in  molar  teeth. 


Fig.  57. — Skull  of  a  new  world  monkey. 


The  old  world  monkey  is  the  first  animal  representing  exactly  the 
dental  formula  of  man  (Fig.  58).     The  three  molars,  the  two  pre- 


00  THE  fMfIt  A^  A  MAStlcATiNG  MACHINE 

molars,  the  canines  and  the  incisors  are  the  same.     There  is,  however, 
a  space  between  the  upper  lateral  incisor  and  the  canine  which  is  to 


^^^^IBB^^^^j^^^H 

^^^^^^^^^^^I^^^^B               ^m''^ 

.'^^,^^^^1 

Hr  1^..,.^  . 

^|pf        '^llMHIii^^^''^ 

__^^^_ 

■•^    "^"T*'"T^jy( 

^^^^^1 

^^^H 

^^k                                                                          ^^M^^^^B 

^^H 

Fig.  58. — Skull  of  an  old  world  monkey. 


Fi.G.  59. — Skull  of  a  chimpanzee,  showing  deciduous  denture- 


^nCONbARY  FUNCTIONS  OF  THE  TEETH 


01 


admit  the  lower  canine.     These  animals  are  largely  frugivorous,  and 
their  teeth  are  suitable  for  this  diet. 

The  hahoon  has  very  long  teeth  and  exactly  the  same  dentition  as 
has  been  seen  before,  that  is,  it  has  the  same  formula.  The  molar 
teeth  are  very  much  the  same  in  general  form  as  the  human  niolars. 
The  chimpanzee  has  a  deciduous  denture  which  is  even  more  like  that 
of  man  (Fig.  59).  The  gorilla  has  a  very  powerful  mandible  and  the 
canines  are  very  strongly  developed. 


Fig.  60. — Architectural  construction  of  skeletal  portion  of  masticating  apparatus: 
the  fixed  base  and  movable  arm.  Columns,  arches  and  buttresses  of  the  fixed  base; 
frontonasal  column,  A  B,  zygomatic  column,  C  M  D,  pterygoid  column  (only  partly 
visible),  supra-orbital  arch,  B  F  D;  infra-orbital  arch,  B  I  D;  upper  nasal  half-arch, 
B  G;  palatal  arch  (not  shown) ;  lower  nasal  arch,  A  H;  large  molar  arch,  A  C;  molar 
buttresses  (descending  from  M) ;  pterygoid  arches  (not  shown) .  Columns  and  arches 
of  the  movable  arm;  mental  column,  N  K;  coronoid  column.  P  Q  0;  and  condyloid 
column,  /  L;  external  oblique  column,  Q  N.  (From  a  photograph  of  specimen  No. 
4237,  Wistar  Institute  of  Anatomy.)      (Turner.) 

It  is  not  such  a  very  long  step  from  the  dentures  of  the  anthropoid 
apes  to  one  of  the  lower  types  of  human  denture  (Fig.  60).  The 
skull  shown  is  not  of  the  lowest  aboriginal  type,  but  the  highly  devel- 
oped jaws  will  be  noted  while  the  skull  case  which  contains  the  brain 
is  not  highly  developed. 

Secondary  Functions  of  the  Teeth. — It  might  be  interesting  to  dwell 
for  a  moment  upon  certain  secondary  functions  developed  in  connec- 
tion with  the  teeth.  Since  secondary  functions  are  performed  by  the 
teeth  of  man,  those  we  find  in  the  animals  may  be  briefly  viewed. 

They  are  used  as  weapons  of  offence,  as  in  the  poison  fangs  of  the 
snake,  which  is  a  very  well-known  example.     The  hypodermic  needle 


92 


THE  TEETH  AS  A  MASTICATING  MACHINE 


really  had  its  origin  in  the  poison  fang  of  the  viperine  snakes,  a  tooth 
with  a  tube  extending  through  its  center  and  leading  to  the  poison 
sac.  Upon  the  contraction  of  the  digastric  muscle  and  opening  of 
the  mouth  the  fang  is  erected,  and  when  it  is  driven  into  the  prey 
the  sac  at  its  base  is  compressed  and  the  poison  injected. 

The  su'ord  fish  has  a  very  dangerous  projection  which  it  uses  to 
open  the  abdomen  of  fish  from  beneath  and  thus  kill  them.  The  use 
of  teeth  as  weapons  in  warfare  is  well  known,  as  in  the  rhinoceros  and 
even  our  domestic  animal,  the  horse.  The  teeth  are  also  used  for 
purposes  of  transportation  and  locomotion.  The  elephant  uses  his 
tusks,  which  are  very  highly  developed  upper  incisors,  to  uproot  trees 
and  dig  up  tuberous  roots.  He  is  trained  in  India  to  use  them  for 
the  purpose  of  transporting  lumber,  etc.  The  walrus  uses  his  upper 
canine  teeth  to  pull  himself  up  on  the  ice,  and  also  for  digging  in  the 
mud  and  uncovering  small  fish,  shell  fish,  etc.,  which  he  consumes. 
One  of  the  most  interesting  of  the  secondary  uses  of  the  teeth  is  found 
in  one  of  the  lemurs.  The  flying  lemur  (galeopithecus  volans)  has 
curious  incisor  teeth,  the  lingual  side  of  which  is  very  much  like  the 
teeth  of  a  comb  and  this  the  animal  uses  to  comb  its  fur. 


Fig.  61. 


-Upper  and  lower  teeth  in  occlusion.     (From  photograph  of  specimen  in 
the  Wistar  Institute  of  Anatomy.) 


The  Human  Dental  Mechanism. — ^The  human  dental  mechanism  pri- 
marily has  to  do  with  the  preparation  of  the  food  for  subsequent 
stages  in  its  digestion,  and  it  is  a  very  interesting  apparatus  viewed 
as  a  machine,  created  for  this  purpose.  To  better  understand  it, 
for  purposes  of  study,  it  may  be  resolved  into  its  various  elements. 
In  the  first  place  it  consists  of  a  fixed  base  and  a  movable  arm  (Fig. 
61).    The  fixed  base  is  the  upper  jaw,  and  the  movable  arm  is  the 


THE  MANDIBLE  93 

lower  jaw.  It  has  been  likened  to  a  hammer  and  anvil  turned  upside 
down;  but  the  metaphor  of  the  fixed  base  and  movable  arm  is  a  little 
more  expressive.  These  two  elements  are  equipped  with  teeth,  the 
armament  of  the  apparatus.  Between  these  two  elements  extend 
the  muscles  which  elevate  the  mandible  and  constitute  the  motive 
power  of  the  machine.  Ordinarily  they  are  spoken  of  as  the  muscles 
of  mastication;  the  masseter,  the  temporal  and  the  two  jAerygoids; 
and  then  at  the  front  end  of  the  mandible  are  muscles  attached  to 
the  genial  tubercles  to  assist  in  lowering  the  mandible,  the  digastric 
and  the  geniohyoid,  and  the  muscle  which  forms  the  floor  of  the  mouth, 
the  mylohyoid.  The  cheeks  and  the  lips  on  the  outside  ser\'e  as  the 
outer  walls  of  the  cavity  which  contains  the  food  while  it  is  being 
masticated.  The  tongue  on  the  inside  is  actively  engaged  in  keeping 
the  food  between  the  crushing  surfaces,  and  assists  the  cheeks  and  lips 
in  that  way.  The  last  element  of  the  apparatus  is  the  salivary  glands, 
the  secretions  of  which  have  both  a  mechanical  and  physiological 
function.  They  lubricate  the  machine,  soften  and  dissolve  the  food 
and  agglutinate  it  for  deglutition,  besides  performing  a  digestive  func- 
tion in  connection  with  the  food. 

The  several  portions  of  the  apparatus  will  be  taken  up  and  discussed 
a  little  more  in  detail.  The  fixed  base,  which  is  the  two  maxillse 
united  in  the  median  line,  is  supported  upon  the  skull  by  a  number  of 
very  strong  columns  or  supports.  It  may  be  better  seen  if  this  base 
is  considered  as  if  it  were  upside  down.  There  are  several  of  these 
bony  columns,  one  going  inside  the  orbit  and  reaching  the  skull  in 
the  median  line  (A  B,  Fig.  60).  There  is  another  one  from  above 
the  first  or  second  molar  going  right  up  through  the  malar  bones  and 
the  outer  border  of  the  eye  {CM  D).  When  the  skull  is  viewed  from 
below  still  another  column  is  seen.  This  is  the  pterygoid,  which 
supports  the  distal  end  of  the  dental  arch. 

The  Mandible. — ^The  lower  jaw  is  the  movable  element,  the  movable 
arm.  It  has  the  general  shape  of  the  letter  "U"  and  the  ends  of 
the  "U"  are  bent  upward  at  the  end  and  terminate  in  the  condyloid 
processes.  There  are  several  layers  of  soft  tissues  intervening  at  the 
joint  which  are  placed  there  to  lessen  the  shock  of  mastication,  and 
permit  the  movement  of  the  joint.  Between  this  point  and  the 
anterior  end  the  muscles  of  mastication  are  attached.  They  move 
the  mandible  as  a  lever,  one  end  of  which  is  fixed  and  constitutes  the 
fulcrum.  The  muscles  are  attached  between  this  end  and  what  is 
the  weight  end  of  the  lever,  the  forward  portion  which  does  the  work. 
Thus  it  is  a  lever  of  the  third  class.  The  fulcrum  exists  in  the  temporo- 
mandibular joint  which  is  interesting  from  a  mechanical  standpoint 
because  it  has  so  much  to  do  with  the  way  in  which  the  mandible 
can  move.  The  form  of  the  glenoid  fossa  is  a  large  factor  in  this. 
The  jaw  cannot  move  backward  but  it  can  move  forward  and  down- 
ward until  it  is  somewhere  near  the  summit  of  the  eminentia  articu- 
laris.    It  can  also  rotate  about  a  horizontal  axis,  passing  approxi- 


94  THE  TEETH  AS  A  MASTICATING  MACHINE 

mately  through  the  condyles.  In  considering  the  manner  of  movement 
of  the  mandible  it  will  be  seen  how  the  joint  renders  these  movements 
possible.  Its  movement  is,  of  course,  limited  by  ligaments.  There 
is  the  ca'psular  ligament  which  is  thickened  at  the  back  into  a  very 
thick  band,  which  prevents  the  jaw  from  going  too  far  forward.  The 
external  and  internal  lateral  ligaments  are  really  nothing  more  or  less 
than  still  greater  thickenings  of  the  capsular  ligament  itself  on  the 
outside  and  inside  of  the  joint  respectively  which  prevent  the  motion 
of  the  jaw  laterally. 

The  other  ligaments,  the  stylomandibular  and  sphenomandihular, 
which  are  largely  thickenings  of  the  cervical  fascia,  do  not  have  very 
much  to  do  with  the  way  with  which  the  mandible  can  move. 

Of  the  muscular  apparatus  it  is  quite  unnecessary  to  speak  exten- 
sively. The  masseter  is  the  muscle  most  concerned  in  the  elevation  of 
the  jaw,  and  the  temporal  and  internal  pterygoid  aid  in  this  movement. 
The  function  of  the  external  pterygoid  must  be  kept  in  mind  in  that 
it  is  attached  to  the  interarticidar  fihrocartilage  as  well  as  to  the  neck 
of  the  condyle,  and  serves  to  pull  them  both  forward  in  the  forward 
movement  of  the  jaw. 

The  direction  in  which  the  mandible  can  move  may  now  be  noted. 
First,  the  simplest  form  of  movement  may  be  taken  up,  starting  from 
that  position  of  the  mandible  in  which  the  teeth  are  in  occlusion. 
This  is  the  point  toward  which  all  the  movements  of  mastication 
ultimately  tend.  With  the  teeth  in  occlusion,  what  happens  when 
the  mandible  is  depressed?  The  external  pterygoid  muscle  on  each 
side  contracts  and  pulls  its  condyle  downward  and  forward.  The 
condyles  slide  down  the  walls  of  the  glenoid  fossae.  The  digastric 
and  geniohyoid  muscles  attached  to  the  genial  tubercles  contract 
and  pull  down  the  front  end  of  the  mandible.  The  effect  of  these 
contractions  is  to  carry  the  front  end  of  the  mandible  down  and 
the  distal  ends  forward.  The  mandible  does  not  rotate  about  a 
fixed  axis,  but  the  condyles  are  being  carried  forward  at  the  same 
time  that  rotation  is  taking  place.  In  other  words,  there  is  a  com- 
bination of  sliding  and  of  rotation,  When  the  mouth  opens  the 
condyles  slide  forward  and  downward,  and  the  front  end  of  the  mand- 
ible is  depressed.  The  mouth  could  not  be  opened  if  the  condyles 
remained  in  the  back  part  of  the  fossse. 

There  is  then  a  combination  of  rotation  about  a  horizontal  axis 
passing  through  the  condyles  and  a  sliding  motion.  It  so  happens 
that  the  front  teeth  describe  what  is  approximately  the  arc  of  a  circle 
while  they  are  sliding  and  rotating;  but  the  center  of  that  circle  is 
not  in  the  condyles,  but  considerably  back  of  them. 

When  the  mandible  is  brought  up  again  to  the  occlusal  position 
the  reverse  of  this  takes  place,  but  Tomes  and  Dolamore  have  found 
out  by  tracing  a  large  number  of  jaws  that  the  path  of  closing  is 
always  a  little  bit  in  front  of  that  of  opening.  Direct  opening  and 
closing  is  a  type  of  movement  seen  in  the  carnivora.    The  condyles 


A  STUDY  OF  THE  HUMAN  DENTURE  95 

do  not  slide  forward.  In  the  herbivorous  animal  there  is  a  lateral 
movement.  In  that  lateral  movement  one  cf)ndyle  remains  in  the 
fossa  and  the  other  one  slides  downward,  forward  and  inward.  This 
type  of  movement  is  al  o  noted  in  the  human  jaw.  One  of  the  con- 
dyles remains  in  its  fossa,  the  other  one  being  pulled  downward  and 
forward  by  the  contraction  of  the  external  jAerygoid  muscle  of  the 
side.  Of  course  that  means  that  the  two  pterygoid  muscles  are 
capable  of  independent  contraction.  The  mandible  rotates  approxi- 
mately about  the  center  of  the  stationary  condyle.  The  same  occurs 
when  the  jaw  moves  to  the  other  side,  as  it  simply  reverses  the  moving 
and  the  stationary  condyles. 

If  both  external  pterygoids  contract,  the  jaw  is  carried  forward  or 
protruded.  If  they  contract  independent  of  the  muscles  attached  to 
the  front  end  of  the  mandible  there  is  a  protrusion  of  the  mandible. 
That  is  a  type  of  movement  characteristic  to  the  rodents  or  the  gnaw- 
ing animals.  There  is  then  in  the  human  jaw  the  possibility  of  these 
three  distinct  types  of  movements. 

Now  that  the  fixed  base  and  the  movable  arm  and  the  motive  power 
of  the  apparatus,  and  the  manner  in  which  the  mandible,  or  the 
movable  element  may  be  actuated  have  been  described,  the  teeth  will 
be  discussed  from  the  standpoint  of  their  form  and  arrangement  as 
suitable  to  the  working  of  the  machine. 

A  Study  of  the  Human  Denture. — In  the  first  place  the  forms  of 
human  teeth  are  modified  or  fused  cones,  as  are  all  animal  teeth  (Fig. 
61).  The  incisors  are  cones  with  a  flattened  end  and  may  be  likened 
to  the  form  of  a  chisel.  This  type  of  a  tooth  is  especially  well  devel- 
oped in  the  rodents.  The  canine  tooth  is  more  nearly  a  cone  of  simple 
form  than  any  other,  although  not  perfectly  circular  in  cross-section. 
It  is  similar  in  general  form  to  the  canine  teeth  in  the  carnivora,  more 
like  them  perhaps  in  a  general  way  than  that  of  any  other  animal 
types,  the  canine  in  the  herbivora  being  either  lacking  or  very  rudi- 
mentary in  character. 

The  bicuspids  (the  term  being  derived,  of  course,  from  their  two- 
cusped  or  two-coned  character)  are,  as  has  been  indicated,  merely  two 
cones  fused  together. 

The  molars,  on  the  other  hand,  have  a  number  of  cones  fused 
together,  each  cone  represented  by  a  cusp;  in  case  of  the  lower  first 
molar  normally  five  cusps,  and  the  others  only  three  or  four. 

The  teeth  are  arranged  in  two  arched  series,  consisting  normally 
of  thirty-two  teeth,  sixteen  in  each  series  (Figs.  62  and  63).  The 
actual  outline  of  this  arch  varies  with  individuals,  but  within  certain 
bounds  this  variation  in  form  has  no  relationship  whatever  to  its 
functional  efficiency. 

The  upper  arch  is  larger  and  overhangs  the  lower.  The  upper  teeth 
constitute  the  fixed  base  in  relation  with  which  the  lower  teeth  move, 
therefore  the  upper  arch  would  necessarily  cover  a  larger  area  in 
order  to  permit  the  movement  of  the  lower  over  its  surface. 


96  THE  TEETH  AS  A  MASTICATING  MACHINE 

On  the  inside  of  the  teeth  is  the  tongue,  on  the  outside  the  lips  and 
cheeks.  The  overhang  of  the  molar  and  bicuspid  series  in  the  rear, 
and  of  the  incisors  in  the  front  of  the  mouth  not  only  serve  the  useful 
purpose  of  providing  a  larger  area  over  which  the  lower  jaw  may  move, 
but  it  serves  to  hold  the  lips  and  teeth  out  of  the  way  and  prevents 


v^aT 

-jH 

-•  ■-  -;  '^^T^ 

l^H^^H 

^^Pl> 

r  «  -'M 

^mt     j^M 

^Li*- 

i 

i^^^l 

p^ 

1^^ 

P^l^,^ 

^^^*^ 

iL 

^ 

^ 

^^  \^  s  ,  **  :t^^M 

Fig.  62. — Occlusal  surfaces  of  the  upper  teeth. 


their  being  caught  between  the  crushing  surfaces.  On  the  inside 
the  fact  that  the  lower  teeth  overlap  and  pass  up  the  inner  sides 
of  the  upper  teeth  serves  a  similar  purpose  of  keeping  the  tongue 
out  of  the  way. 


Fig.  63. — Occlusal  surfaces  of  the  lower  teeth. 

One  may  realize  how  useful  this  provision  is  if  one  observes  a  set  of 
artificial  teeth  in  which  this  overhang  is  not  properly  provided,  when 
the  wearer  will  frequently  complain  that  he  bites  his  cheeks.  Instances 
of  the  same  difficulty  are  seen  in  mouths  with  full  sets  of  natural  teeth, 
the  cusps  of  which  have  worn  down,  and  in  which  the  lower  jaw  has 
moved  forward  to  what  is  designated  an  edge-to-edge  bite.    There  is 


OCCLUSION  97 

no  doubt  of  the  authenticity  of  the  reported  case  (^f  a  well-known  man 
who  lost  his  life  through  cancer  originating  in  the  irritation  of  the 
cheek  from  biting  it  when  the  cusps  of  his  teeth  had  worn  (jff  until  he 
had  an  edge-to-edge  bite. 

The  series  of  teeth  normally  present  an  unbroken  surface  from 
one  end  around  to  the  other;  that  is,  there  are  no  spaces  between 
them,  as  in  some  of  the  animals,  particularly  the  carnivorous  animals. 
Man  is  the  only  animal  not  having  diastemata,  or  spaces  between 
his  teeth.  This  is  provided  for  by  the  bell-like  shape  of  the  crowns 
of  the  teeth  which  do  not  touch  at  their  necks  but  at  the  point  of 
interproximal  contact.  This  contact  serves  to  protect  the  gum  tissue 
below  from  injury  from  the  food  such  as  meat  and  vegetable  fibers. 
If  one  has  experienced  what  it  is  in  one's  own  denture  to  have  a  flat 
filling,  or  none  at  all,  in  consequence  of  w^hich  food  packs  in  and 
produces  the  long  train  of  uncomfortable  results,  one  will  understand 
how  wise  is  this  provision  of  nature. 

Occlusion. — The  occlusion  of  the  teeth,  to  attempt  a  very  offhand 
definition,  is  the  relationship  of  their  morsal  surfaces  when  the  man- 
dible is  in  the  position  of  the  resting  bite  (Fig.  64).  The  phrase  is 
used  to  indicate  the  relationship  of  the  upper  and  lower  teeth  w^hen 
in  such  contact  that  there  is  a  definite  fitting  together  of  their  surfaces. 
In  the  occlusal  position  the  condyles  of  the  mandible  are  in  the  most 
distal  part  of  the  glenoid  fossae.  When  the  teeth  are  in  occlusion  the 
muscles  extending  between  the  jaw^s  are  either  in  a  state  of  tonic 
contraction,  simply  holding  the  jaw  up,  or  they  may  be  actively  con- 
tracted, that  is,  pressing  the  lower  teeth  firmly  upon  the  upper  ones. 
This  is  a  rather  fundamental  position  of  the  jaw.  It  is  a  position  of 
equilibrium.  It  is  to  this  position  and  from  this  position  that  all 
the  various  movements  incident  to  mastication  take  place.  In  the 
crushing  of  the  food  the  jaw  tends  to  return  from  its  various  excursions 
to  the  occlusal  position. 

The  occlusion  of  the  teeth  then  means  the  definite  relationship 
existing  between  the  occlusal  or  morsal  surfaces  of  the  teeth.  This 
must  be  carefully  considered,  for  in  order  to  understand  the  machine 
in  motion  it  must  first  be  studied  in  repose.  Perhaps  simplicity  will 
be  consulted  by  dividing  the  description  of  the  occlusion  into  that  of 
the  incisor  teeth,  and  that  of  the  molar  and  bicuspid  teeth. 

As  to  the  incisors,  which  are  flat  and  wedge-shaped,  the  upper 
overhang  the  lower,  the  incisal  edges  of  the  lower  resting  normally 
in  contact  with  the  lingual  or  inside  surfaces  of  the  upper  teeth.  This 
normal  overhang  or  overbite  is  approximately  one-third  of  the  length 
of  the  lower  teeth,  although  of  course  it  is  subject  to  slight  variation. 
The  canine  tooth  is  really  intermediate  in  the  character  of  its  occlu- 
sion between  the  incisor  and  the  bicuspid  series.  It  partakes  of  the 
characteristics  of  the  incisors  in  that  it  overhangs  the  lower  teeth, 
but  it  is  like  the  bicuspids  in  having  a  sharp  cusp  exactly  like  the 
buccal  cusps  of  the  bicuspids. 
7 


98  THE  TEETH  AS  A  MASTICATING  MACHINE 

When  the  teeth  have  worn  down  either  from  having  had  a  very 
small  overbite  and  short  cusps  originally,  or  from  the  use  of  coarse 
food,  so  that  there  is  an  edge-to-edge  bite,  the  machine  is  by  no  means 
as  effective  as  in  the  arrangement  referred  to  as  normal.  In  the  latter 
case  the  food  is  simply  pinched  off  and  not  sheared  off  as  when  the 
upper  incisors  overhang. 

In  the  study  of  the  occlusion  of  the  molar  and  bicuspid  series  of 
teeth  the  occlusal  surfaces  should  be  first  considered  (Figs.  62  and 
63) .  It  will  be  noted  that  they  exhibit  two  rows  of  cones  with  depres- 
sions or  fossae  intervening  between  them.  On  this  surface  of  the 
bicuspids  there  is  a  cone  on  the  inner  and  outer  side.  In  studying 
the  molars  there  will  be  found  two  cones  on  the  inner  and  outer  sides, 
except  on  the  third  molar  where  the  distolingual  cusp  may  be  lacking. 

There  are  then  a  row  of  inner  and  a  row  of  outer  cones,  with  fossse 
or  little  pits  intervening  between  them.  There  are  transverse  ridges 
dividing  one  fossa  from  another.  The  same  thing  is  true  of  the 
occlusal  surfaces  of  the  lower  series  of  teeth.  They  have  a  definite 
arrangement,  a  row  of  outer  and  a  row  of  inner  cusps  with  fossae 
between.  However,  there  is  a  difference  in  the  shape  in  these  two 
rows  of  cusps.  The  inner  ones  are  rounded  in  the  upper  series  of 
teeth  and  are  considerably  larger  than  those  in  the  outer  row.  Speak- 
ing technically,  the  lingual  are  larger  than  the  buccal  cusps,  which 
are  sharp  and  thin,  while  the  reverse  of  this  is  true  of  the  lower  teeth. 
The  buccal  cusps,  or  outer  cones,  are  the  large  round  ones;  the  inner 
cusps  are  sharp  and  thin.  The  rounded  cusps  in  both  series  are  really 
the  functionating  cusps.  They  are  the  ones  which  are  received  into 
the  fossae  when  the  teeth  are  in  the  occlusal  position.  If  an  upper 
set  of  teeth  is  superposed  upon  a  lower,  it  will  be  found  that  the  lower 
buccal  cusps  occupy  the  fossae  of  the  upper  series  and  the  rounded 
lingual  cusps  of  the  upper  fit  into  the  fossae  in  the  lower  set  of  teeth. 

It  is  not  enough  in  the  normal  arrangement  that  any  cusp  should 
fit  into  any  fossa.  In  normal  occlusion  there  is  a  definite  fossa  for 
each  cusp  to  occupy  (Fig.  64) .  Orthodontists  have  accepted  a  simple 
method  of  determining  when  a  denture  is  in  normal  occlusion.  They 
look  to  see  if  the  mesiobuccal  cusp  of  the  first  upper  molar  occupies 
the  buccal  groove  of  the  first  lower  molar  and  if  so  and  the  other 
cusps  fit  into  their  fossae,  and  so  on,  then  the  occlusion  is  correct.  If 
this  cusp  is  in  front  of  or  back  of  the  buccal  groove  then  it  would 
not  be  normal  occlusion;  there  might  be  an  interdigitation  of  the 
cusps,  but  it  would  not  be  perfectly  normal  unless  each  cusp  occupied 
its  own  particular  fossa. 

In  an  inner  view  of  the  denture  (Fig.  65),  the  overlapping  of  the 
sharp  and  thin  inner  cusps  of  the  lower  teeth  will  be  noted,  each 
fitting  into  a  groove  or  space  on  the  liiigual  surfaces  of  the  upper 
teeth.  This  interdigitation  has  also  another  rather  interesting  advan- 
tage, and  this  is  that  each  tooth  of  both  series,  with  two  exceptions, 
js  opposed  b^  two  teeth  in  the  opposite  iaw.    They  do  not  meet  en4 


OCCLUSION 


99 


Fig.  64. — Occlusion  of  the  molar  and  bicuspid  teeth,  external  view.      (From  photograph 
of  a  specimen  in  possession  of  Dr.  F.  A.  Peeso.) 


Fig.  65. — Occlusion  of  the  molar  and  bicuspid  teeth,  internal  view.    (From  photograph 
pf  a  specimen  in  possession  of  Dr.  F.  A.  P^eso.^ 


100 


THE  TEETH  AS  A  MASTICATING  MACHINE 


on  end,  but  each  tooth  is  in  relation  to  two  teeth.  The  exceptions 
are  the  upper  third  molar  and  the  lower  central  incisor  which  have 
but  one  opponent  each  (Fig.  66). 


Fig.  66. — Occlusion  of  the  molar  and  bicuspid  teeth,  occlusal  view.  Lines  are  drawn 
from  the  lingual  cusps  of  the  upper  teeth  and  buccal  cusps  of  the  lower  to  the  correspond- 
ing depressions  into  which  they  fit.  (From  photograph  of  a  specimen  in  possession  of 
Dr.  F.  A.  Peeso.) 

Now  that  the  relationship  of  the  morsal  or  occlusal  surfaces  of  the 
teeth  in  the  position  of  occlusion  has  been  described,  it  will  often  be 
referred  to  as  the  occlusion  of  the  teeth. 


Fig.  67. — The  "  Curve  of  Spee."     Line  passing  through  anterior  face  of  condyle, 
a  photograph  of  a  specimen  in  the  Wistar  Institute  of  Anatomy.) 


(From 


There  are  certain  other  characteristics  of  the  arrangement  of  the 
occlusal  surfaces  of  the  teeth  which  are  related  to  what  shall  be  spoken 


OCCLUSION     ^  101 

of  as  the  articulating  or  active  relations  of  the  denture  that  will  be 
useful  when  the  denture  is  in  motion.  One  of  these  characteristics, 
which  is  a  very  iniportant  part  in  the  so-called  articulation  of  the 
teeth,  is  as  follows:  If  an  imaginary  line  were  drawn  touching  the 
buccal  cusps  of  the  lower  series  of  teeth  in  a  perfect  denture,  it  would 
be  found  that  they  described  approximately  the  arc  of  a  circle,  and 
if  it  is  continued  backward  under  a  perfectly  typical  arrangement,  it 
passes  just  anterior  to  the  articulating  face  of  the  condyle  (Fig.  67). 
Sometimes  this  line  may  go  a  little  in  front  of  it,  more  frequently  it 
is  back  of  the  condyle;  in  a  perfect  arrangement  it  passes  through 
the  anterior  face  of  the  condyle.  The  same  thing  is  necessarily  true 
of  the  upper  teeth.  This  is  called  the  curve  of  Spee.  It  has  been 
named  after  von  Spee  who  first  called  attention  to  it.  This  curved 
arrangement  of  the  occlusal  surfaces  of  the  molar  and  bicuspid  teeth 
has  an  important  bearing  on  the  movement  of  the  mandible. 

If  two  surfaces  are  to  slide  one  upon  the  other  without  interrupting 
their  contact  at  any  point,  that  is,  without  being  separated  at  any 
point,  these  must  be  either  two  perfectly  flat  surfaces  like  two  panes 
of  plate  glass,  where  one  can  slide  upon  the  other  without  admitting 
air  underneath,  or  else  two  curved  surfaces  which  are  the  arcs  of  the 
same  circle.  If  they  were  any  other  shape,  as  for  example,  a  parabola 
or  hyperbola,  or  any  irregular  curve,  they  would  separate  at  some 
point.  Now  if  it  were  desirable  that  in  the  forward-and-backward 
movement  of  the  mandible  all  of  the  lower  teeth  should  slide  upon  all 
of  the  upper  at  the  same  time,  then  these  teeth  would  have  to  be 
either  in  a  perfectly  plane  surface,  all  absolutely  level,  or  they  would 
have  to  be  arranged  around  the  arc  of  a  circle. 

In  order  to  get  a  clearer  understanding  of  this,  it  may  be  supposed 
that  there  are  no  cusps  upon  the  occlusal  surfaces  and  that  a  curved 
line  represents  the  top  surface  of  the  lower  teeth,  and  a  similar  curved 
line  represents  the  occlusal  surfaces  of  the  upper  teeth.  Now  if  these 
surfaces  are  to  slide  upon  each  other,  without  breaking  their  contact, 
in  the  case  of  the  human  jaw  the  mandibular  condyles,  which  of 
course  slide  upon  the  glenoid  fossse,  would  have  to  slide  in  exactly 
that  same  curve,  otherwise  the  teeth  would  be  separated  at  some 
point. 

Now  this  is  the  significance  of  this  arrangement  of  the  teeth,  that 
the  so-called  curve  of  Spee  is  always  either  continuous  with  the  path 
of  the  condyle,  or  it  is  concentric  with  it;  at  any  rate  they  can  both 
move  around  the  same  center.  This,  it  must  be  remembered,  is 
merely  a  very  much  simplified  example  taken  to  explain  the  principle 
involved.  These  are  not  plane  surfaces,  but  are  cuspid  surfaces, 
and  each  one  of  these  cusps  fits  into  a  fossa.  However,  it  does  not 
take  a  very  great  stretch  of  imagination  to  see  that,  though  they 
have  cuspid  surfaces,  the  cusps  may  be  arranged  so  that  instead  of 
sliding  upon  a  smooth  surface  they  slide  upon  the  walls  of  the  fossae 
into  which  they  fit.     That  it  is  possible  to  have  such  an  arrangement 


10^ 


THE  TEETH  AS  A  MASTICATING  MACHINE 


may  be  conceived  and  this  is  the  arrangement  in  the  perfectly  typical 
and  typal  human  denture.  Of  course  the  mandible  has  to  be  depressed 
the  least  bit  in  order  to  enable  each  cusp  to  slide  downward  on  the 
front  wall  of  the  fossa  into  which  it  fits.  The  cusps  slide  forward  on 
the  walls  of  the  fossse  and  back  again;  and  the  advantage  of  this  is 
that  every  one  of  the  cusps  is  functionating,  is  in  contact  at  the  same 
time,  not  just  hitting  here  or  there.  But  it  is  possible  for  a  denture 
to  functionate  in  this  fashion  only  if  the  teeth  are  arranged  in  the 
manner  described. 

It  will  presently  be  seen,  however,  that  the  lower  teeth  of  a  normal 
typical  denture  cannot  slide  very  far  forward  without  the  teeth  sepa- 
rating, because  the  lower  incisors  strike  the  lingual  surfaces  of  the 


Fig.  68. — Upper  and  lower  bicuspid  and  molar  teeth  (side  view),  showing  relative 
height  of  buccal  and  lingual  cusps  of  upper  teeth.  (From  photograph  of  a  specimen  in 
the  Wistar  Institute  of  Anatomy.) 


upper  incisors.  After  the  cusps  have  moved  perhaps  half-way  up  the 
walls  of  the  fossse  into  which  they  fit,  the  lower  front  teeth  strike  the 
upper  incisors  upon  which  they  slide  and  the  distal  teeth  are  separated. 
But  in  the  return  movement,  when  the  lower  teeth  strike  the  lingual 
surface  of  the  upper  and  slide  up  until  the  distal  teeth  are  in  contact 
and  then  slide  back  into  the  occlusal  position,  each  one  of  the  cusps 
then  slides  back  down  the  wall  of  its  fossa  into  the  position  of  the 
occlusion. 

There  is  another  characteristic  of  the  arrangement  of  the  molar 
and  bicuspid  teeth  which  is  related  to  the  lateral  excursion  of  the 
jaw.  Taking  a  typically  perfect  set  of  teeth  with  the  jaws  slightly 
apart,  it  will  be  seen  that,  starting  from  the  first  upper  bicuspid  and 
going  toward  the  rear,  the  buccal  or  outer  cusps  become  relatively 


OCCLUSIOM  '  lOr^ 

a  little  bit  shorter  than  the  hngual  cusps  and,  in  the  case  of  the  lower 
teeth,  they  become  a  little  longer  than  the  lingual  cusps.  Of  the 
second  bicuspid  in  the  upper  jaw,  the  buccal  and  lingual  cusps  nor- 
mally occupy  the  same  horizontal  plane.  Just  in  front  of  it  the  first 
bicuspid  has  a  buccal  cusp  that  is  longer  than  the  lingual.  Return- 
ing to  the  first  molar,  the  buccal  cusps  are  a  little  shorter  than  the 
Hngual,  and  going  back  farther  and  farther,  they  get  relatively  shorter 
than  the  lingual.  In  other  words,  the  plane  of  the  cusps,  instead  of 
being  level,  gradually  curves  rootword  and  outward  toward  the  rear 
of  the  denture   (Fig.  68). 


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Fig.  69. — Lower  bicuspid  and  molar  teeth,  front  view,  showing  relative  height  of 
buccal  and  lingual  cusps.  Same  mandible  as  Fig.  68.  (From  photograph  of  a  speci- 
men in  the  Wistar  Institute  of  Anatomy.) 

This  arrangement  can  be  demonstrated  in  the  mandible  although 
the  first  bicuspid  has  a  rudimentary  cusp  or  none  at  all  and  is  atypical 
in  this  particular;  but  farther  back  the  buccal  cusps  are  relatively 
higher  than  the  lingual  until  at  the  third  molar  they  are  considerably 
higher  (Fig.  69). 

In  looking  at  the  upper  teeth  this  characteristic  may  not  be  so  well 
illustrated  as  in  the  lower  jaw,  but  a  gradual  tilting  out  of  the  long 
axes  of  the  teeth  will  be  noted.  This  arrangement  is  due  not  only 
to  the  height  of  the  cusps,  but  to  a  change  in  the  inclination  of  the 
teeth.  The  second  bicuspid  occupies  a  perpendicular  position;  but 
the  teeth  back  of  it  gradually  tilt  outward. 


104  THE  TEETH  AS  A  MASTICATING  MACHINE 

Now  what  is  the  relationship  of  this  arrangement  to  the  lateral 
excursion  of  the  lower  jaw?  When  the  mandible  is  moved  to  one  side 
with  the  teeth  in  contact,  if  the  teeth  were  arranged  so  that  their 
cusps  occupied  the  same  horizontal  plane  those  on  one  side  would  be 
separated  while  those  on  the  other  side  would  be  in  contact.  The 
reason  for  this  is  that  when  the  mandible  is  carried  to  one  side  one 
condyle  remains  stationary  in  its  fossa  while  the  other  is  pulled  for- 
ward and  also  downward  as  the  surface  of  the  glenoid  fossa  inclines 
downward  and  this  side  of  the  jaw  must  be  carried  a  little  lower  than 
the  side  with  the  stationary  condyle. 

If  it  were  not  for  this  difference  in  the  level  of  the  buccal  and  lingual 
cusps  there  would  be  a  lack  of  contact  on  the  side  from  which  the 
movement  was  taking  place.  In  order  to  compensate  for  this  lower- 
ing of  the  mandible  on  the  side  from  which  the  movement  has  taken 
place,  the  two  longest  or  most  prominent  cusps  come  into  contact; 
whereas  on  the  other  side,  the  side  toward  which  the  movement  has 
taken  place,  there  is  a  short  and  long  cusp  in  contact;  and  it  is  just 
the  difference  between  these  two  which  compensate  for  the  down- 
ward movement  of  the  jaw  on  the  side  from  which  the  movement  has 
occurred  (Fig.  70). 


Fig.  70. — Diagram  illustrating  contact  of  cusps  in  lateral  excursion  of  the  mandible. 
Section  through  jaws  at  position  of  second  molar.  O  P,  line  touching  lingual  cusps  of 
upper  molars ;  L  R,  line  touching  buccal  cusps  of  upper  molars ;  *S  T,  line  touching  buccal 
cusps  of  lower  molars,  showing  the  downward  movement  of  the  mandible  on  the  right 
side  necessary  for  contact  of  the  cusps. 

What  is  the  advantage  of  this  arrangement?  It  has  exactly  the 
same  functional  advantage  in  the  lateral  excursion  of  the  mandible 
as  the  curve  of  Spee  affords  in  the  forward  and  backward  excursion 
of  the  jaw;  that  is  to  say,  it  enables  both  sides  to  be  in  contact  at 
the  same  time.  This  principle  is  taken  advantage  of  in  making 
artificial  dentures.  If  both  sides  of  the  plates  were  not  in  contact 
at  the  same  time,  so  that  the  patient  was  biting  foods  on  one  side 
with  the  other  side  not  touching  at  all,  the  plates  would  be  thrown 
down  from  their  base.  So  it  is  desirable  to  imitate  the  human  denture 
in  this  particular  because  it  prevents  overstrain  and  provides  a  denture 
that  is  more  efficient  mechanically. 

There  is  one  other  detail  of  the  occlusal  surfaces  of  these  teeth 
relating  to  their  function  which  must  be  mentioned  and  this  is,  that 


MASTICATION  OF  FOOD  105 

clearance  spaces  are  provided  for  the  escape  of  fo(jd  which  lias  been 
masticated.  The  upper  row  of  buccal  cusps  overhangs  the  lower, 
and  on  the  outer  walls  of  all  of  these  fossa%  into  which  the  lower 
buccal  cusps  fit,  are  grooves  leading  downward  and  outward  through 
which  the  food  is  squeezed.  Anyone  operating  a  cutting  or  grinding 
machine  of  any  kind  will  realize  the  necessity  of  getting  rid  of  the 
waste  or  the  chip,  as  the  mechanical  terminology  is.  That  is,  after 
the  substance  has  been  crushed  or  ground,  there  must  be  an  avenue 
of  escape  for  the  waste,  and  so  these  grooves,  which  are  not  visible 
on  the  side  view,  but  which  lead  downward  on  the  outside  of  the  arch, 
and  upward  on  the  inside,  are  provided.  When  the  food  is  crushed 
between  these  surfaces  it  is  carried  up  above  the  tongue  on  the  inside 
and  downward  into  the  pocket  of  the  cheek  on  the  outside  where  it 
may  be  pressed  between  the  teeth  when  they  are  separated  for  the 
next  crushing  motion. 

Mastication  of  Food. — Having  described  the  machine,  its  mode  of 
operation  may  now  be  considered.  In  the  case  of  man  the  prepara- 
tion of  food  in  the  mouth  does  not  begin  with  prehension  or  gripping 
of  the  food,  as  it  does  in  most  of  the  lower  animals.  Man  has,  of 
course,  developed  very  much  beyond  that  point,  and  there  is  no  neces- 
sity for  it.  There  is  no  provision  for  this  in  his  denture  therefore, 
and  he  has  no  sharp  teeth  to  prehend  the  food.  The  first  act  of  the 
human  animal  is  to  incise;  but  even  incision  or  the  cutting  off  of 
appropriately  sized  particles  of  food  is  largely  rudimentary  in  man, 
since  with  the  development  of  conventional  methods  of  eating,  bringing 
into  use  the  knife  and  fork,  the  incisor  teeth  are  not  much  exercised. 
The  biting  of  certain  articles  of  food  only  is  permitted  by  the  usages 
of  polite  society.  But  when  incision  is  indulged  in  it  is  rather  an 
interesting  mechanical  act.  The  lower  jaw  is  depressed  and  carried 
forward,  the  food  is  pressed  between  the  lips  and  upon  the  incisal 
edges  of  the  upper  teeth,  when  the  lower  jaw  is  carried  upward.  If 
the  food  is  very  hard,  the  ends  of  the  upper  and  lower  teeth  are  almost 
exactly  opposite  each  other.  This  direct  opposition  is  absolutely 
necessary  from  a  mechanical  standpoint,  in  order  to  bite  through 
hard,  resistant  food.  As  soon,  however,  as  the  teeth  come  into 
contact,  or  nearly  into  contact,  the  mandible  is  carried  backward  as 
well  as  upward,  and  the  lower  incisors  slide  up  the  inner  surface  of 
the  upper,  just  like  the  blades  of  a  pair  of  shears.  Then  the  food  is 
carried  back  by  the  tongue  to  the  distal  part  of  the  mouth. 

In  order  to  understand  clearly  just  what  is  demanded  during  trit- 
uration of  the  food,  it  will  he  wise  to  refer  again  to  the  importance 
of  a  knowledge  of  the  character  of  the  food  itself.  Its  chemical 
nature  is  not  of  so  much  interest  as  its  physical  character  viewed 
purely  from  a  mechanical  standpoint.  Man's  food,  broadly  speak- 
ing, consists  of  meat  fiber,  vegetable  fiber,  grain  or  cereals  and  foods 
made  from  them  and  legumes,  although  the  last  is  not  of  the  same 
importance  as  the  others.     The  chief  articles  which  must  be  pre- 


106  TUB  TEETH  AS  A  MASTICATING  MACHINE 

pared  for  digestion  are  vegetable  and  meat  fibers,  cereals  or  grain. 
It  is  necessary  to  reduce  this  food  to  a  condition  suitable  for  passage 
into  the  stomach.  Its  physical  consistence  must  be  reduced  that  it 
can  be  acted  upon  by  the  digestive  ferments  and  solvents.  The 
crushing  of  grain,  the  starchy  element  of  man's  food  must  be  very 
much  more  extensive  than  is  necessary  for  the  other  elements.  In 
the  first  place,  its  outer  covering  has  to  be  removed,  or  at  least  broken, 
and  the  grains  of  starch  themselves  must  be  so  ground  up  that  they 
can  be  acted  upon  by  the  enzyme  of  the  mouth,  and  by  those  farther 
down  in  the  digestive  tract.  Mastication  of  cereals  and  foods  made 
from  them  is  therefore  really  much  more  important  than  the  mastica- 
tion of  other  foods. 

Baron  Oefele  has  conducted  some  investigations  to  show  the  very 
poor  ability  to  digest  cereals  exhibited  by  people  who  do  not  have  a 
full  complement  of  molar  and  bicuspid  teeth.  His  results  are  very 
interesting,  but  it  is  only  necessary  for  our  purpose  to  state  the  fact 
that  he  has  very  conclusively  shown  the  defective  digestion  of  cereals 
by  those  whose  molar  and  bicuspid  teeth  are  defective. 

Vegetable  fibers  must  be  cut  up  into  short  lengths  and  crushed  so 
that  they  can  be  readily  acted  upon  by  the  solvents  and  digestive 
ferments.  This  is  more  important  than  the  comminution  of  meat 
fibers.  Many  carnivorous  animals  eat  animal  flesh  in  great  masses; 
carnivorous  snakes  always  swallow  their  prey  whole.  Nevertheless 
it  is  important  that  meats  should  be  masticated  by  man  in  order 
to  break  up  the  consistence  of  the  fiber,  and  also  it  should  be  cut  up 
into  small  masses  to  facilitate  its  passage  through  the  digestive  tract 
and  that  it  may  be  readily  acted  upon  by  the  enzymes  and  ferments 

Dr.  Black,  who  has  investigated  quite  extensively  the  problem  of 
the  mastication  of  the  various  kinds  of  foods,  is  authority  for  the 
statement  that  the  up-and-down  movements  of  the  jaw,  very  much 
like  those  of  the  carnivorous  animals,  are  chiefly  concerned  in  the 
mastication  of  meats,  and  that  the  lateral  movements  are  chiefly 
concerned  in  the  mastication  of  cereals  and  foods  made  from  them. 

While  it  is  not  true  that  in  the  masticating  of  any  type  of  food 
one  is  limited  to  any  particular  type  of  movement,  it  is  a  fact  that 
the  foods  which  require  the  greatest  amount  of  crushing  force  are 
masticated  in  the  return  from  the  lateral  excursion  of  the  mandible. 

When  the  cereal  food  is  brought  into  the  mouth  and  carried  back 
to  the  molar  and  bicuspid  teeth,  mastication  usually  occurs  on  one 
side  at  a  time;  and  if  the  mouth  is  in  a  state  of  balance  and  perfect 
health,  it  is  very  apt  to  occur  first  on  one  side  and  then  on  the  other. 
The  mandible  is  carried  to  one  side,  the  cusps  are  brought  into  con- 
tact, some  of  the  food  being  cut  off  on  the  outside  and  some  on  the 
inside,  but  a  mass  remains  which  occupies  the  space  between  the 
cusps  and  in  the  fossse  and  on  the  return  to  the  position  of  occlusion 
the  cusps  slide  into  the  fossse  with  a  sort  of  mortar-and-pestle  effect. 
In  this  movement  the  greatest  crushing  ability  is  exhibited.     In 


MASTICATION  OF  FOOD  107 

ordinary  mastication  this  lateral  movement  is  combined  with  direct 
up-and-down  movement.  Mastication  is  not  carried  on  in  any  precise 
mechanical  order,  but  all  of  the  movements  are  combined  at  times. 

Dr.  Black  has  also  made  in  this  connection  what  is  rather  an  inter- 
esting table  of  the  amount  of  force  necessary  to  crush  the  various 
foodstuffs.  Dr.  Joseph  Head,  of  Philadelphia,  has  also  produced 
a  similar  table,  though  using  a  different  method,  and  the  two  will 
be  presented  together.  Dr.  Black's  experiments  were  most  interest- 
ing. He  had  some  brass  castings  made  of  the  molar  and  bicuspid 
series  of  teeth,  upper  and  lower,  and  had  them  arranged  in  a  machine 
so  that  the  lower  could  be  brought  up  into  contact  with  the  upper 
by  the  movement  of  a  hand  lever:  This  simply  had  the  up-and-down 
motion.  He  and  a  party  of  friends  went  at  various  times  to  restau- 
rants in  Chicago,  and  while  they  were  dining  themselves,  they  gave 
this  automatic  chewing  machine  various  tidbits,  and  registered  on  it, 
as  they  could  not  on  their  own  jaws,  the  amount  of  force  necessary 
to  crush  the  various  foodstuff's. 

Dr.  Head,  realizing  the  value  of  the  lateral  excursion,  and  believing 
that  much  less  force  was  required  in  the  crushing  of  food  with  this 
type  of  movement,  made  experiments  similar  to  those  of  Dr.  Black, 
except  that  he  took  a  human  skull  with  a  fine  set  of  teeth  and  turned 
it  upside  down,  bored  a  hole  through  the  skull,  and  suspended  weights 
from  the  mandible  by  means  of  string  or  wire.  He  proved  that  to 
accomplish  the  same  amount  of  crusHing,  less  force  was  required  in 
this  lateral  sliding  movement.  Dr.  Black's  and  Dr.  Head's  tables 
are  here  given. 

Dr.  Head's  Dr.  Black's 

results.  results. 

Raw  cabbage 16  40-60 

Raw  onion 4 

Head  lettuce 8  25-30 

Radish— whole 20-25 

Radish— pieces 10-25  3&-40 

Corned  beef 18-20  30-35 

Boiled  beef 3 

Tongue ' 1-2  3-5 

Lamb  chops 16-20 

Roast  lamb .  4 

Roast  lamb  kidney 3 

Tenderloin  of  beefsteak  (very  tender) ....        8-9  35-40 

Sirloin  steak   .      .      .      .      : 10-20-43 

Round  of  beefsteak  (tough) 38-42  60-80 

Roast  beef 20-35  35-50 

Boiled  ham 10-14  40-60 

Pork  chops 10-13 

Roast  veal 16  35-40 

Veal  chops 12 

Roast  mutton .,     18-22 

Very  tough  meats 90 

Hard  crusts 100 

Hard  candy 250 

Dr.  Black  also  experimented  with  a  gnathodynamometer  by  means 
of  which  he  could  measure  the  strength  exerted  by  the  human  dental 


108  THE  TEETH  AS  A  MASTICATING  MACHINE 

mechanism,  which  for  the  average  was  from  150  to  175  pounds.  He 
reported  one  case  in  which  275  pounds  were  recorded  on  the  instru- 
ment. He  also  tried  it  with  persons  wearing  full  artificial  dentures, 
upper  and  lower,  the  result  being  that  the  average  was  from  35  to  40 
pounds.  One  may  see  a  vast  difference  in  the  amount  of  crushing 
ability  of  natural  and  artificial  teeth. 

Mastication  is,  of  course,  a  voluntary  act  (speaking  physiologically), 
that  is,  it  begins  voluntarily  and  is  continued  reflexly  and  automatic- 
ally. The  food  is  rolled  from  one  side  to  the  other  by  the  tongue. 
The  teeth  functionate  first  on  one  side  and  then  on  the  other.  The 
teeth  have  exquisite  sensibility.  It  is  through  them  that  sensations 
are  received  that  indicate  the  amount  of  chewing  necessary  to  give 
any  given  mouthful,  and  also  through  them  in  conjunction  with  the 
tongue  as  to  whether  the  food  has  been  thoroughly  triturated  or  not. 
After  it  has  been  thoroughly  masticated  it  is  rolled  up  into  a  bolus  on 
the  tongue,  the  tip  of  which  is  elevated,  and  by  contraction  of  the 
muscle  of  the  floor  of  the  mouth,  the  mylohyoid,  the  food  is  forced 
back  into  the  esophagus. 

The  secretion  of  the  saliva,  while  constantly  going  on  in  the  mouth, 
is  tremendously  increased  when  any  foreign  substance,  like  food,  is 
put  into  the  mouth.  The  working  of  the  muscles  moving  the  jaw 
probably  also  increases  the  flow  of  saliva.  The  saliva  serves  to  lubri- 
cate the  various  portions  of  the  apparatus  which  are  in  the  mouth. 
It  contains  a  ferment^  ptyalin,  which  has  some  digestive  usefulness. 
The  water  in  the  saliva  dissolves  some  of  the  food,  and  as  it  also 
contains  mucin,  the  latter  helps  to  agglomerate  the  mass  and  to 
lubricate  it  so  that  it  is  finally  easily  swallowed. 

The  teeth  are  equipped  with  means  of  resisting  the  wear  incident 
to  the  activity  of  this  mechanism.  The  enamel  is  the  outer  envelope 
of  the  crowns  of  the  teeth  and  is  the  hardest  structure  in  the  human 
body.  It  is  of  course  necessary  to  have  a  very  hard  covering  for  the 
teeth  to  enable  them  to  resist  the  wear  incident  to  their  long  use. 
Under  present  conditions  of  civilization,  where  comparatively  little 
mastication  is  necessary,  not  a  great  deal  of  wear  of  the  teeth  occurs. 
The  teeth  of  prehistoric  man,  and,  indeed,  of  our  own  aboriginal  races, 
wore  very  badly  from  the  coarse  character  of  the  food.  Any  collec- 
tion of  skulls  of  North  American  Indians  which  one  may  happen  to 
see  at  once  impresses  one  with  the  great  amount  of  wear  of  these 
teeth.  Of  course  this  is  due,  not  only  to  the  rough  character  of  the 
food,  but  also  to  the  fact  that  Indian  corn,  a  staple  diet,  being  ground 
in  stone  mortars  had  fine  particles  of  stone  or  silica  mixed  with  it, 
which  serve  to  grind  the  teeth  down. 

Anatomists  have  recognized  several  degrees  of  wear.  No  one 
reaches  the  age  of  twenty-five  without  beginning  to  show  some  evi- 
dence of  wear  of  the  teeth.  A  little  later  the  second  degree  is  reached, 
where  the  enamel  is  worn  through  and  the  dentin  exposed,  and  the 
cusps  are  really  beginning  to  wear  down  a  little;  or  it  may  even,  under 


SUPPLEMENTARY  FUNCTIONS  OF  THE  TEETH 


109 


conditions  of  our  civilization,  get  to  the  third  degree,  where  the  cusps 
are  all  worn  away  and  the  teeth  are  reduced  in  height. 

Mastication  has  also  a  beneficial  influence  upon  the  teeth.  The 
friction  of  the  food  exerts  a  cleansing  influence  as  regards  colonies 
of  bacteria  and  deleterious  food  particles  upon  their  surface.  Disuse 
of  the  teeth  on  the  other  hand,  greatly  increases  the  deposits  of  sali- 
vary calculus  and  sordes  upon  the  teeth.  Often  upon  looking  into 
a  mouth  it  is  perfectly  easy  to  judge  upon  which  side  a  crippled  tooth 
exists,  because  when  the  chewing  is  done  on  the  other  side,  exclu- 
sively, deposits  on  the  teeth  of  the  crippled  side  identify  it. 

The  use  of  the  denture  in  mastication  also  exercises  the  peridental 
membrane.     As  the  teeth  move  up  and  down  in  their  sockets,  blood 


T&D7b 


K&a 


Fig.  71. — 1,  diagrammatic  drawing,  showing  place  of  articulation  of  the  consonant 
sounds;  2,  drawing  showing  contact  of  the  tongue  with  molars  and  bicuspids  in  the 
formation  of  certain  consonants. 


is  pumped  in  and  out  of  this  tissue  and  thus  it  is  kept  in  a  healthy 
condition  and  degeneration  of  the  pericementum  is  deferred  if  not 
prevented. 

Supplementary  Functions  of  the  Teeth. — In  conclusion,  certain  second- 
ary functions  of  the  teeth  will  be  briefly  considered.  They  participate 
in  the  activity  of  the  mechanism  concerned  in  the  production  of 
speech.  The  lips  and  tongue  with  the  teeth  and  the  contiguous 
portions  of  the  alveolar  process  are  the  most  important  factors  in 
the  production  of  consonant  sounds.  Thus  the  "F"  and  "V"  sounds, 
for  example,  are  pronounced  by  the  sudden  escape  of  air  between 
the  lower  lip  and  the  upper  front  teeth.  It  is  unnecessary  to  go  into 
this  detail  at  length,  but  an  allusion  is  made  to  it  as  an  additional 
reason  for  care  in  the  preservation  of  the  teeth  (Fig.  71). 


no 


THE  TEETH  AS  A  MASTICATIXG  MACHIXE 


§'&>' 


J 


Fig.  ~1. — The  facial  muscles  of  expression. 


Pjq  73 — Photograph,  showing  effect 
of  the  loss  of  the  teeth  upon  the  mouth, 
and  wrinkles  established  thereby. 


Fig.  74. — Photograph,  showing  the 
effects  of  the  loss  of  the  teeth  upon  thg 
profile. 


SUPPLEMENTARY  FUNCTIONS  OF  THE  TEETH  111 

They  are  also  passive  elements  in  the  mechanism  concerned  with  the 
facial  movements  of  expression,  which  are  movements  of  the  facial 
muscles  that  either  supplement  language  or  convey  ideas  or  emotions 
or  states  of  mind. 

The  underlying  structures  in  this  mechanism  are  the  skull  and  the 
teeth,  overlying  which  are  soft  tissues  including  the  facial  muscles  of 
expression.  There  is  a  large  group  of  these  centering  around  the 
mouth  which  makes  it  one  of  the  most  expressive  features  of  the 
face.  These  muscles  are  superficial,  converge  toward  the  mouth  and 
terminate  in  one  big  muscle,  the  orbicularis  oris,  of  which  latter  the 
lips  are  chiefly  composed.  These  are  all  supported  beneath  by  the 
teeth  and  the  alveolar  process,  over  which  as  a  sort  of  base  they  are 
moved  by  these  various  muscles.  In  some  of  these  movements  the 
lips  are  parted  so  that  the  teeth  are  disclosed.  Both  pleasurable  and 
painful  emotions  may  be  so  expressed  (Fig.  72).* 

Finally  the  teeth  serve  to  support  the  lips  and  the  cheeks  and  thus 
take  part  in  the  maintenance  of  the  fixed  expression  of  the  face. 
Their  loss  is  attended  by  a  falling  in  of  these  tissues,  an  approxima- 
tion of  the  jaws,  and  by  a  marked  change  in  the  appearance  in  the 
face.  To  guard  against  this  "last  scene  of  all"  is  the  final  reason 
for  their  preservation  (Figs.  73  and  74). 


CHAPTER  IV. 
MALOCCLUSION  OF  THE  TEETH. 

By  RODRIGUES  OTTOLENGUI,  M.D.S.,  D.D.S.,  LL.D. 

If  the  mouth  hygienist,  besides  preservmg  the  health  of  her  charge, 
would  aim  likewise  to  guard  against  the  attacks  of  disease,  it  is  evi- 
dent that  she  should  have  knowledge  of  such  diseases  as  may  prove 
a  menace  in  her  particularly  field  of  work,  and  she  should  likewise 
learn  to  recognize  these  diseases  in  their  incipient  stages  that  she 
may  refer  the  patient  for  treatment  before  the  ravages  prove  serious. 

Therefore,  in  presenting  the  subject  of  malocclusion,  let  us  con- 
sider for  a  moment  how  dental  caries  is  aggravated  by  irregular  or 
malposed  teeth, 

DENTAL  CARIES. 

Areas  of  Susceptibility. — Students  of  the  subject  tell  us  that  in  the 
vast  majority  of  cases  caries  begins  in  certain  definite  localities. 
Thus  caries  upon  the  masticating  surfaces  of  bicuspids  and  molars 
first  appears  in  the  sulci  or  fissures  between  the  enamel  plates. 
Between  the  teeth  or,  as  we  say,  on  the  approximal  surfaces,  caries 
has  its  initiation  at,  or  just  gingival  to,  the  approximal  contact 
points.  While  it  may  not  be  absolutely  true  that  "a  clean  tooth 
never  decays,"  it  is  true  than  an  unclean  tooth  is  more  vulnerable 
than  one  that  is  clean.  It  follows,  therefore,  that  the  unclean  or 
uncleansable  parts  of  a  tooth  are  more  likely  to  decay  than  the  clean 
or  readily  cleansable  parts  of  a  tooth,  and  this  is  in  consonance  with 
the  statements  above  made  as  to  the  locations  where  caries  usually 
begins,  because  the  sulci  of  molars  and  bicuspids,  and  the  approximal 
contact  points  of  all  teeth,  are  the  localities  in  which  food  debris  is 
most  apt  to  lodge  and  most  difficult  to  dislodge.  Another  region  in 
which  caries  often  occurs  is  upon  the  labial  and  buccal  surfaces  of 
teeth  immediately  near  the  gum  line.  Here  the  seepage  of  mucus 
agglutinizes  the  food  debris  and  the  overhanging  gum  margins  pro- 
tect the  accumulations  from  the  natural  cleansing  agents.  Still 
another  place  is  in  the  grooves  on  the  buccal  surfaces  of  the  molars, 
which  are  analogous  with  the  sulci  upon  the  masticating  surfaces. 
These,  then,  are  to  be  counted  the  vulnerable  places. 

Areas  of  Immunity. — The  lingual  surfaces  of  all  the  teeth,  swept  as 
they  are  by  the  tongue,  constitute  the  most  immune  areas,  though 
occasionally  we  find  pits  or  crevices  in  the  upper  incisors,  which 
because  they  are  pits  or  crevices  become  susceptible  points.    The 


DENTAL  CARIES  113 

labial  surfaces  of  all  incisors  and  cuspids,  except  at  or  along  the  gum 
margins,  and  the  buccal  surfaces  of  all  bicuspids  and  molars,  exept  in 
the  molar  buccal  grooves  and  along  the  gum  margins,  are  practically 
immune  to  caries. 

So  we  find  that  there  are  certain  localities  which  are  vulnerable 
and  other  definite  parts  of  the  tooth  which  are  practically  immune 
to  caries.  Also,  that  this  immunity  is  closely  related  to  the  possi- 
bility of  cleansing  these  areas. 

Between  these  vulnerable  and  immune  locations  are  areas  of  com- 
parative immunity,  this  comparative  immunity  increasing  toward  the 
immune  or  most  easily  cleansed  part,  and  decreasing  as  we  approach 
the  vulnerable  or  less  easily  cleansed  part. 

Caries  and  Malocclusion. — ^Thus  we  arrive  at  the  important  relation 
between  malocclusion  and  caries.  We  have  seen  that  certain  parts 
of  the  teeth  are  counted  to  be  immune  to  caries,  and  that  adjacent 
to  these  areas  are  other  parts  which  are  comparatively  immune.  But 
this  is  true  only  when  all  the  teeth  are  in  normal  relationship  one 
with  the  other,  which  in  effect  means  when  all  the  teeth  are  in 
normal  occlusion. 

Malocclusion  may  not  perhaps  often  increase  the  vulnerability  of 
the  occlusal  surfaces  of  the  teeth,  though  at  times  it  may  even  have 
this  effect;  but  malposition  of  the  teeth  will  frequently  increase  the 
vulnerable  approximal  areas  by  increasing  the  contactual  areas  beyond 
the  normal;  and  it  will  likewise  lessen  the  immunity  of  the  immune 
and  comparatively  immune  areas,  by  rendering  cleansing  more  difficult 
and  at  times  even  impossible. 

We  will  better  comprehend  this  by  the  examination  of  a  skull  where 
we  may  see  the  teeth  and  bones  freed  from  the  soft  tissues. 

Interproximal  Spaces. — ^Fig.  75  affords  a  good  example  of  normally 
occluded  teeth,  one  maxilla  and  one-half  of  the  mandible  with  their 
teeth  being  shown.  Attention  should  be  called  first  to  the  spaces 
between  the  teeth  known  as  interproximal  spaces.  Note  that  these 
are,  generally  speaking,  trangular  in  shape,  the  base  of  the  triangle 
being  along  the  border  of  the  alveolar  bone,  the  sides  of  the  triangle 
being  the  approximal  surfaces  of  the  adjacent  teeth,  and  the  apex 
at  the  point  of  contact  of  the  two  teeth.  Select  any  approximal 
space  distal  of  the  cuspids  and  note  that  the  apex  of  the  cusp  of  the 
antagonizing  tooth  of  the  opposing  jaw  falls  immediately  opposite 
the  center  of  this  interproximal  space,  the  obvious  tendency  being  to 
force  food  between  the  teeth,  and  into  this  interproximal  space. 
Hence  the  need  of  the  contact  point.  Passing  from  the  study  of  these 
bones  and  examining  a  living  specimen,  we  would  observe  that  this 
interproximal  space  is  filled  with  gum  tissue,  this  particular  part  of 
the  gum  being  denominated  the  septum.  This  septum,  filling  as  it 
does  a  triangular  space,  is  conical  in  shape  and  is  thicker  than  other 
parts  of  the  gum.  For  this  reason  its  outer  surface  is  farther  away 
from  its  bony  support  and  consequently  it  is  more  easily  injured  than 


114 


MALOCCLUSION  OF  THE  TEETH 


the  gum  elsewhere.  This  is  an  added  need  for  close  contact  of  the 
adjacent  teeth,  as  a  protection  to  this  sensitive  tissue  from  the  impac- 
tion of  food  and  the  retention  of  it,  if  forced  into  the  interproximal 
space.  The  student  should  note  also  that  the  gum  septum,  also 
called  the  gingiva,  even  in  the  healthiest  subject,  does  not  entirely 
fill  the  interproximal  space,  so  that  commonly  there  is  a  small  but 
actual  space  between  the  approximal  contact  points  and  the  septum 
or  gingiva.  It  is  because  of  this  fact  that  approximal  caries  often 
has  its  inception  just  gingivally  of  the  contact  point,  since  it  is  just 
in  this  space  which  is  protected  from  the  natural  cleansing  agencies 
that  debris  may  collect  and  remain. 


Fig.  75. — Occlusion  of  the  molar  and  bicuspid  teeth,  external  view.     (From  photograph 
of  a  specimen  in  possession  of  Dr.  F.  A.  Peeso.) 


If  we  study  the  matter  more  closely  still,  we  must  see  that  wise 
provision  has  been  made  for  the  exclusion  of  foodstuffs  from  the 
interproximal  spaces.  True,  the  grinding  cusps  of  the  masticating 
teeth,  falling  as  they  dp  exactly  opposite  to  the  entrances  to  the 
interproximal  spaces,  would  seem  to  be  advantageously  situated  for 
the  forcing  of  food  into  these  spaces,  yet  this  accident  is  well  guarded 
against.  First  we  find  that  the  cusps  in  typically  formed  teeth  occlude 
with  the  mesial  and  distal  marginal  ridges  of  the  two  teeth  with 
which  each  cusp  normally  antagonizes.    These  marginal  ridges  have 


DENTAL  CARIES  115 

planes  sloping  toward  the  central  portions  of  the  masticating  surfaces, 
and  hence  away  from  the  interproximal  space. 

Moreover  we  find  sulci  serving  as  sluiceways  to  lead  the  food, 
during  maceration,  lingually  and  buccally  away  from  the  spaces 
between  the  teeth,  and  consequently  it  should  require  more  force  to 
crowd  the  food  into  the  interproximal  spaces  than  away  from  them 
into  and  out  of  the  sluiceways.  Additional  protection  of  the  gingivae 
is  to  be  found  in  the  form  and  position  of  the  contacts,  as  well  as  in 
the  form  of  the  septum  itself.  The  contacts  are  closest  occlusally 
and  triangular  in  shape  so  that  the  width  of  the  contacts  increase 
slightly  toward  the  gingiva,  while  the  approximal  surfaces  of  the 
teeth,  curving  rapidly  apart,  afford  ample  opportunity  for  the  escape 
of  food,  especially  as  the  septum  itself  is  conical  and  full  enough 
bucco-lingually  to  extend  somewhat  beyond  the  actual  interproximal 
space  and  thus  aid  in  receiving  and  carrying  the  food  away  from, 
rather  than  into,  the  space. 

All  this  may  seem  somewhat  complex,  whereas  in  reality  when  once 
fully  comprehended,  it  will  be  seen  to  be  quite  simple  and  as  admirable 
an  arrangement  as  it  is  a  simple  one.  Yet  its  efficiency  depends  entirely 
upon  and  is  proportional  with  its  typical  normality.  Any  aberration 
from  the  typical  in  the  formation  of  the  teeth,  and  any  departure  from 
the  normal  in  the  position  of  the  teeth,  must  proportionately  destroy 
the  balance  between  the  several  factors  which,  when  present  and 
working  in  unison,  will  afford  ample  protection  to  even  this  vulnerable 
locality. 

Contact  Point  in  Normal  Arrangement. — Glancing  again  at  Fig.  75, 
the  student  is  asked  to  note  that  the  teeth  being  in  normal  arrange- 
ment, the  contacts  are  at  a  minimum,  while  yet  being  sufficient  to 
afford  protection.  Since  caries  starts  at  these  points  of  contact,  it 
must  be  manifest  that  any  malposition  of  the  teeth  which  will  bring 
into  contact  a  greater  area  than  normally  should  be  in  contact,  not 
only  increases  the  actual  area  of  the  vulnerable  region,  but  by  altering 
the  protective  form  of  the  contact  points,  must  necessarily  add  also 
to  the  vulnerability.  In  Fig.  75  note  also  that  as  each  tooth  is  in  its 
normal  pose  the  greater  portion  of  its  exposed  surface  is  brought  into 
symmetrical  alignment  with  its  neighbors,  so  that  any  cleansing  agency 
sweeping  around  the  arch  would  come  into  touch  with  and  conse- 
quently would  cleanse  the  greatest  width  of  such  surface.  Thus, 
where  teeth  are  normally  placed,  a  brush  passing  around  the  arch 
would  cleanse  nearly  all  the  labial  an4  buccal  enamel,  while  a  brush 
passed  vertically  over  these  surfaces  would  cleanse  them  entirely.  An 
examination  of  the  lingual  surfaces  (Fig.  76)  discloses  the  fact  that 
the  truly  normal  arrangement  again  brings  beneath  the  influence  of 
a  cleansing  agent  the  widest  expanse  of  surface. 

It  is  equally  evident  that  any  malposition  of  even  a  single  tooth 
must  interfere  with  this  cleansing  effort.  If  a  tooth  be  turned  upon 
its  axis,  then  a  smaller  part  of  its  labial  or  buccal  surface  can  be 


116 


MALOCCLUSION  OF  THE  TEETH 


swept  by  the  brush  when  the  brush  is  used  upon  that  part,  and  the 
same  would  be  true  when  brushing  the  Ungual  surfaces.  If  a  tooth 
extends  beyond  its  neighbors,  either  buccally  or  lingually,  not  only 
will  it  become  more  difficult  to  cleanse  that  particular  tooth,  but  its 
position  must  interfere  more  or  less  with  the  cleansing  of  its  neighbors. 
It  is  seen  then  that  any  aberration  from  the  normal  in  the  inter- 
relation of  the  teeth  renders  them  more  difficult  to  keep  clean,  but  it 
must  be  understood  that  aside  from  the  artificial  cleansing  which  is 
to  be  accomplished  with  brushes,  powders,  etc.,  the  typical  forms  and 
arrangement  of  the  teeth  are  such  that  the  normal  use  of  these  organs 
leaves  them  moderately  clean,  so  that  the  teeth  in  ideal  normal  occlu- 


FiG.  76.— Occlusion  of  the  molar  and  bicuspid  teeth,  internal  view.     (From  photograph 
of  a  specimen  in  possession  of  Dr.  F.  A.  Peeso.) 

sion  are  said  to  be  "self-cleansing,"  this  cleansing  being  accomplished 
by  the  lips,  the  tongue,  and  by  the  food  passing  over  the  surfaces  of 
the  teeth. 

Terms  Defined. — Occlusion:  The  relation  between  the  upper  and 
lower  teeth  when  the  jaws  are  closed. 

Arch:    A  term  used  to  designate  the  upper  or  lower  teeth  collectively. 

Inclined  Plane:    The  sloping  surface  of  a  cusp. 

Mesial,  Dvital:  Position  is  considered  in  relation  to  the  median 
line  or  center  of  the  dental  arches.  Hence,  "mesial"  means  toward  or 
nearest  to  the  median  line,  and  "distal '  means  away  from  or  farthest 
from  the  median  line. 


A  STUDY  OF  NORMAL  OdCLUHION  117 

Model:  A  reproduction  of  the  dental  arch  or  arches  made  in  plaster 
of  Paris. 

Labial:    Toward  the  Hps. 

Buccal:    Toward  the  cheek. 

Limjval:  Toward  the  tongue.  This  term  is  used  to  describe  the 
upper  as  well  as  the  lower  teeth. 

Protruding:  The  tipping  of  the  axis  of  a  tooth  so  that  the  crown 
projects  labially  to  normal. 

Retrudmg:  The  tipping  of  the  axis  of  a  tooth  so  that  the  crown 
slants  lingually  to  normal. 

A  STUDY  OF  NORMAL  OCCLUSION. 

Before  the  student  can  comprehend  any  description  of  malocclusion 
he  must  acquire  a  knowledge  of  normal  occlusion.  He  should  be  able 
mentally  to  visualize  a  set  of  teeth  in  normal  occlusion,  as  a  standard 
picture  with  which  to  compare  any  set  of  teeth  under  examination, 
in  order  instantly  to  detect  deviations  from  the  normal. 

Definition. — Normal  occlusion  is  the  normal  relation  of  the  occlusal 
inclined  planes  of  the  teeth  when  the  jaws  are  closed  (Angle). 

As  occlusion  means  the  relation  between  the  upper  and  lower  teeth 
when  the  jaws  are  closed,  it  follows  that  normal  occlusion  means  that 
all  the  teeth  in  both  arches  are  so  situated  that  they  may  best  perform 
their  functions,  and  that  their  interrelation  shall  be  typical  and 
therefore  normal. 

In  a  set  of  teeth  in  normal  occlusion  the  teeth  themselves  are  arranged 
in  symmetrical  parabolic  curves,  commonly  called  arches.  This  means 
that  if  a  line  be  drawn  across  either  arch,  so  as  to  touch  the  distal  sur- 
faces of  the  last  molars,  and  a  second  line  be  drawn  at  right  angles 
thereto  and  through  the  median  space,  or  between  the  central  incisors, 
then  any  two  similar  teeth  on  opposite  sides  of  the  arch  (as  for  example 
the  first  bicuspids)  will  be  equidistant  from  this  central  line. 

Perhaps  the  next  most  noteworthy  fact  is  that  the  upper  arch  is 
slightly  larger  than  the  lower,  and  that  the  outer  cutting  edges  and 
cusps  of  the  upper  teeth  droop  over  and  consequently  hide  in  part  the 
similar  portions  of  the  lower  teeth  when  the  jaws  are  closed  (Fig. 
75).     This  latter  condition  is  called  the  "overbite." 

In  full  denture  there  are  thirty-two  teeth.  In  the  illustration  which 
depicts  one-half  of  an  upper  and  lower  jaw  we  should  see  sixteen  teeth; 
but,  as  a  matter  of  fact,  the  artist  in  endeavoring  to  expose  the  full 
surface  of  the  upper  central  incisor  has  so  turned  the  subject  that  in 
the  lower  arch  we  see  an  extra  tooth,  the  lower  central  incisor  of  the 
opposite  side.  Mentally  eliminating  this  extra  tooth,  by  studying 
the  illustration  we  observe  that  the  smallest  incisor  is  the  central 
incisor  in  the  lower  arch,  while  the  smallest  molar  is  the  last  or  third 
molar  in  the  upper  arch.  It  is  in  accordance  with  Nature's  wonderful 
design,  which  aims  to  produce  the  highest  efficiency  in  the  use  of  the 


118  MALOCCLUSION  OP  THE  TEETH 

teeth  collectively  as  a  masticating  apparatus,  that  this  is  true,  for  by 
this  means  every  other  tooth  except  these  four  occludes  with  two 
others.  Again  glancing  at  the  illustration  we  see  that  the  lower 
lateral  incisor  is  in  contact  with  the  upper  central  and  lateral;  the 
upper  central  touches  the  low^er  central  and  lateral;  the  upper  lateral 
antagonizes  the  lower  lateral  and  cuspid,  and  so  on  around  the  arch, 
each  tooth  of  either  upper  or  lower  jaw  occluding  with  two  teeth  in 
the  opposing  jaw.  The  most  important  usefulness  of  this  arrangement 
is  seen  when  we  consider  those  teeth  which  have  cusps.  For  example, 
observe  the  first  upper  bicuspid,  occluding  with  the  cuspid  and  bicuspid 
of  the  lower  arch.  Any  food  caught  in  this  locality  is  triturated 
between  three  powerful  cusps,  a  much  more  effective  plan  than  were 
each  tooth  to  strike  only  one  antagonist,  as  sometimes  occurs  where 
malocclusion  is  present. 

This  at  once  brings  us  to  one  diagnostic  point.  It  being  a  fact  that 
in  normal  occlusion  all  the  teeth  except  the  lower  central  incisors  and 
upper  third  molars  occlude  so  that  each  tooth  antagonizes  two,  we 
note  that  the  only  place  in  the  entire  denture  where  the  interproximal 
spaces  coincide  is  at  the  median  line.  Two  facts  then  may  be  remem- 
bered. Whenever  any  interproximal  spaces  above  and  below  coincide 
(except  these  at  the  median  line),  malocclusion  exists.  Conversely, 
whenever  the  spaces  at  the  median  line  do  not  coincide,  malocclusion 
is  present. 

We  should  next  consider  those  teeth  which  are  supplied  with  cusps, 
viz.,  the  cuspids,  the  bicuspids  and  the  molars.  In  regard  to  the  cus- 
pids and  bicuspids,  when  in  normal  occlusion  the  crest  or  extreme 
angle  of  the  cusp  should  be  exactly  in  line  with  the  interproximal 
space  between  the  two  teeth  with  which  it  occludes.  Or  to  phrase  it 
differently,  a  line  drawn  through  the  central  axis  of  a  cuspid  or  bicus- 
pid should  pass  between  the  two  antagonizing  teeth. 

In  all  the  teeth  which  have  cusps,  including  the  molars,  each  cusp 
has  four  slanting  surfaces  called  inclined  planes;  note  that  of  these  the 
mesial  inclined  planes  of  the  cusps  of  the  upper  teeth  occlude  with  the 
distal  inclined  planes  of  the  cusps  of  the  lower  teeth;  and  of  course 
the  distal  inclined  planes  of  the  upper  cusps  touch  the  mesial  inclined 
planes  of  the  lower  teeth. 

As  will  be  seen  presently,  however,  a  point  of  extreme  significance, 
because  used  so  often  as  a  basis  of  diagnosis,  is  the  occlusal  relation 
of  the  upper  and  lower  first  molars.  The  student  therefore  should 
become  thoroughly  familiar  with  this  cusp  relation  (Fig.  75).  The 
upper  molar  has  two  buccal  cusps,  known  as  the  mesio-buccal  cusp 
and  the  disto-buccal  cusp.  In  normal  occlusion  the  mesio-buccal  cusp 
of  the  upper  first  molar  occludes  between  the  mesio-buccal  and  buccal 
cusps  of  the  lower  first  molar,  in  such  a  manner  that  the  crest  or 
extreme  point  of  the  cusp  coincides  with  a  groove  in  the  buccal  surface 
of  the  lower  tooth,  known  as  the  buccal  groove.  It  is  well  also  to 
observe  that  the  mesio-buccal  cusp  of  the  lower  molar  occludes  in 


MALOCCLUSION  110 

part  with  the  similar  cusp  of  the  upper  molar  and  in  part  with  the 
upper  second  bicuspid;  also  that  the  extreme  mesial  surface  of  the 
lower  molar  is  on  a  line  with  the  central  axis  of  the  upper  second 
bicuspid.  Attention  is  called  to  this  fact  here,  as  it  will  be  again 
elsewhere,  because  while  in  the  normal  relation  the  lower  first  molar 
is  slightly  mesial  of  the  upper  first  molar,  it  should  not  be  farther 
forward  than  the  median  axis  of  the  upper  second  bicuspid. 

A  study  of  the  same  set  of  teeth  from  the  lingual  aspect  (Fig.  76) 
shows  similar  interlocking  of  the  teeth  and  the  general  appearance  is 
the  same  except  that  here  it  is  the  cusps  and  incisal  ends  of  the  upper 
teeth  that  are  slightly  hidden  in  consequence  of  the  overbite,  the 
converse  of  what  is  true  of  the  buccal  view  (Fig.  75). 

Summary. — 1.  Where  teeth  are  in  normal  occlusion  they  are  arranged 
in  symmetrical  parabolic  curves  and  any  two  similar  teeth  on  opposite 
sides  of  an  arch  will  be  equidistant  from  the  central  line,  or  axis. 

2.  The  upper  arch  is  larger  than  the  lower  and  the  cusps  of  the  upper 
teeth  droop  over  the  lower.     This  is  denominated  the  overbite. 

3.  With  the  exception  of  the  two  lower  central  incisors  and  the 
two  upper  third  molars,  each  tooth  in  each  arch  antagonizes  with  two 
teeth  of  the  opposite  arch  when  in  occlusion. 

4.  The  interproximal  space  at  the  median  line  above  and  below 
should  coincide.  When  they  do  not,  or  when  any  other  interproximal 
spaces  do  coincide,  a  malrelation  of  the  arches  is  present. 

5.  A  line  drawn  vertically  through  the  median  axis  of  any  cuspid 
or  bicuspid  should  pass  between  the  antagonizing  teeth. 

6.  The  mesial  inclined  plane  of  any  cusp  occludes  against  the  distal 
inclined  plane  of  the  opposing  cusp;  the  converse  therefore  is  likewise 
true. 

7.  In  normal  occlusion  the  mesio-buccal  cusp  of  the  upper  first  molar 
occludes  between  the  mesio-buccal  and  buccal  cusps  of  the  lower  first 
molar. 

MALOCCLUSION. 

Definition. — ^Any  deviation  of  the  teeth  or  arches  from  normal 
relation  is  termed  malocclusion. 

Malocclusion  of  Individual  Teeth. — A  tooth  may  occupy  any  one  of 
seven  malpositions,  and  it  is  even  possible  for  it  to  be  malposed  in 
four  ways. 

These  malpositions  have  been  named  as  follows  (Angle) :  (1)  Labial 
or  buccal  occlusion;  (2)  lingual  occlusion;  (3)  mesial  occlusion;  (4) 
distal  occlusion;  (5)  supra-occlusion;  (6)  infra-occlusion;  (7)  torso- 
occlusion. 

1.  Labial  or  buccal  occlusion  means  that  a  tooth  crown  is  so  mal- 
posed that  it, is  labial  or  buccal  of  its  true  normal  position. 

2.  Lingual  occlusion  means  that  a  tooth  crown  is  so  malposed  that 
it  is  lingual  of  its  true  normal  position. 


120  MALOCCLUSION  OP  THE  TEETH 

3.  Mesial  occlusion  means  that  a  tooth  crown  is  mesial  of  the  posi- 
tion which  it  should  normally  occupy. 

4.  Distal  occlusion  means  that  a  tooth  crown  is  distal  of  the  position 
which  it  should  normally  occupy, 

5.  Supra-occlusion  means  that  a  tooth  has  erupted  to  an  abnormal 
height  in  its  socket. 

6.  Infra-occlusion  means  that  a  tooth  has  not  erupted  to  a  normal 
height  in  its  socket. 

7.  Torso-occlusion  means  that  a  tooth  is  turned  in  its  socket  so 
that  it  does  not  occupy  its  normal  place  in  the  arch  alignment. 

In  explanation  of  the  statement  that  a  single  tooth  may  be  in  four 
positions  of  malocclusion  at  one  and  the  same  time,  I  would  cite  the 
following  example:  A  molar  tooth  may  be  in  torso-occlusion;  in 
buccal  or  lingual  occlusion;  in  mesial  or  distal  occlusion;  in  supra-  or 
infra-occlusion. 

Classification  of  Malocclusion. — It  is  manifest,  therefore,  that  there 
are  endless  varieties  of  malocclusion  when  viewed  in  the  light  of 
single  or  multiple  malpositions  of  the  individual  teeth.  It  remained 
for  Angle,  however,  to  discover  the  possibility  of  formulating  a  classi- 
fication for  malocclusion,  independent  of  these  individual  malposi- 
tions but  based  upon  the  relations  of  the  two  arches  considered  as 
units.  Other  writers  have  endeavored  to  erect  classifications  which 
do  depend  upon  the  individual  malpositions,  but  in  none  of  these  is 
the  line  of  demarcation  between  the  described  classes  so  well  drawn 
that  it  may  serve  as  an  absolute  division  between  the  multiplicity  of 
conditions  that  arise.  The  result  is  that  often  cases  are  found  which 
might  fall  into  either  of  two  such  classes  or  even  into  both.  For 
example,  we  have  had  classes  for  "outstanding  cuspids" — cases  where 
the  cuspids  have  erupted  labially  of  normal.  Again,  classes  of  "open 
bite,"  meaning  an  infra-occlusion  or  lack  of  antagonization  of  the 
incisors.  What  are  we  to  do  then  with  a  case  where  we  have  "out- 
standing cuspids"  complicated  with  "open  bite?"  In  the  Angle 
classification  no  such  confusion  can  occur.  His  lines  of  demarcation 
are  so  distinct,  that  there  can  be  no  lapping  of  boundaries. 

Of  his  classification  Angle  writes:^  "These  classes  are  based  on 
the  mesio-distal  relations  of  the  teeth,  dental  arches  and  jaws,  which 
depend  primarily  upon  the  positions  mesio-distally  assumed  by  the 
first  permanent  molars  on  their  erupting  and  locking.  Hence,  in 
diagnosing  cases  of  malocclusion  we  must  consider  first,  the  mesio- 
distal  relations  of  the  jaws  and  dental  arches,  as  indicated  by  the 
relation  of  the  lower  first  molars  with  the  upper  first  molars,  the  keys 
to  occlusion;  and  second,  the  position  of  the  individual  teeth,  care- 
fully noting  their  relations  with  the  line  of  occlusion." 

Angle  then  has  divided  all  malocclusion  into  three  great  classes 
dependent  upon  the  mesio-distal  relations  of  the  arches  considered 

1  Angle,  Seventh  edition,  p.  35. 


MALOCCLUSION  121 

as  units.  It  is  evident,  then,  that  to  make  a  diagnosis,  we  must 
always  begin  with  a  picture  of  normal  molar  occlusion  in  the  mind, 
and  with  the  question,  "Is  the  mesio-distal  relation  of  the  molars 
normal  on  both  sides?"  The  answer  to  this  mental  question  will 
invariably  classify  the  case. 

To  have  such  a  mental  picture  w^e  must  carefully  study  normal 
molar  relations,  as  shown  in  Fig.  75,  noting  that  the  mesio-buccal  cusp 
of  the  upper  first  molar  occludes  with  the  lower  first  molar  in  such  a 
way  that  a  line  drawn  through  the  apex  of  this  cusp  will  fall  directly 
into  the  buccal  groove  of  the  lower  molar.  Or  to  phrase  it  differently, 
the  mesio-buccal  cusp  of  the  upper  first  molar  occludes  between  the 
mesio-buccal  and  buccal  cusps  of  the  lower  first  molar,  whereas  the 
mesio-buccal  cusp  of  the  lower  first  molar  occludes  between  the  mesio- 
buccal  cusp  of  the  upper  molar  and  the  buccal  cusp  of  the  upper 
second  bicuspid.  Thus  we  see  that  the  mesial  surface  of  the  lower 
first  molar  is  normally  slightly  mesial  to  the  corresponding  surface 
of  the  upper  first  molar.  Hence,  in  studying  mesial  occlusion  of  the 
lower  first  molar,  it  is  important  to  recognize  the  limitations  of  the 
normal  mesial  position  of  this  surface  in  relation  with  that  of  its 
antagonists.  When  the  cusps  are  not  mutilated  by  caries  or  bad 
fillings,  however,  we  may  confine  ourselves  to  an  examination  of  the 
cusp  relations. 

The  Angle  Classification. — In  studying  a  case,  if  we  find  that  the 
mesio-distal  relations  of  the  upper  and  lower  first  molars  on  both  sides 
are  normal,  the  malocclusion  belongs  in  Class  I. 

If  the  lower  first  molar  on  one  or  both  sides  is  found  to  be  distal  to 
normal  in  relation  wdth  the  upper  first  molar,  it  is  said  to  be  in  distal 
occlusion,  and  the  malocclusion  falls  into  Class  11. 

If  the  lower  first  molar  on  one  or  both  sides  is  found  to  be  mesial  to 
normal  in  relation  with  the  upper  first  molar,  it  is  said  to  be  in  mesial 
occlusion,  and  the  malocclusion  falls  into  Class  III. 

The  distinctions,  therefore,  between  Classes  I,  II  and  III  are  very 
definite  and  should  be  readily  comprehended.  Some  confusion  has 
been  caused  in  the  minds  of  beginners  by  the  fact  that  there  are 
divisions  and  subdivisions,  but  these  likewise  may  be  so  plainly 
described  that  there  should  be  no  difficulty  whatever.  Once  having 
learned  to  distinguish  between  Classes  I,  II  and  III,  we  next  learn 
that  there  are  no  divisions  in  Class  I  nor  in  Class  III.  But  Class  II 
is  separated  into  two  divisions:  Division  1,  wherein  the  upper  inci- 
sors protrude,  and  Division  2,  wherein  the  upper  incisors  retrude.  These 
are  the  sole  factors  by  which  the  divisions  of  Class  11  are  determined, 
and  there  remains  no  more  to  learn  except  the  subdivisions.  A  sub- 
division is  any  case  of  malocclusion  where  the  mesiodistal  relations 
of  the  upper  and  lower  first  molars  is  normal  on  one  side  and  abnormal 
on  the  other.  If  the  abnormality  be  a  distal  occlusion,  the  case  must 
be  a  subdivision  of  Class  II,  because  all  cases  of  distal  occlusion  are 
in  Class  II.     If  the  abnormality  be  a  mesial  occlusion  the  malocclu- 


m 


MALOCCLUSION  OF  THE  TEST  It 


sion  must  belong  to  Class  III  because  all  mesial  occlusions  are  in 
Class  III. 

The  following  recapitulation  of  the  classification  is  copied  from 
Angle,  omitting  his  references  to  etiological  factors  with  which  we 
are  not  at  the  moment  interested: 

Class    I.      Arches  in  normal  mesio-distal  relation. 
Class  II.      Lower  arch  distal  to  normal  in  its  relation  to  the  upper 
arch. 
Division  1.      Bilaterally  distal,  protruding  upper  incisors. 
Subdivision.    Unilaterally  distal,  protruding  upper  incisors. 
Division  2.      Bilaterally  distal,  retruding  upper  incisors. 
Subdivision.    Unilaterally  distal,  retruding  upper  incisors. 
Class  III.    Lower  arch  mesial  to  normal  in  its  relation  to  the  upper 
arch. 
Subdivision.    Unilaterally  mesial. 


Fig.  77. — Models  of  a  case  of  malocclusion,  Class  I. 


To  fix  the  differentiations  of  this  classification  more  firmly  in  the 
mind  let  us  examine  the  illustrations  of  a  few  typical  cases.  In  Fig. 
77,  an  examination  of  the  first  molars  discloses  that  on  each  side  the 
mesio-distal  occlusal  relations  are  normal.  On  each  side  the  mesio- 
buccal  cusp  of  the  upper  first  molar  occludes  between  the  cusps  of  the 
lower  first  molar,  and  a  line  drawn  through  the  central  axis  of  the 
mesio-buccal  cusp  of  the  upper  molar,  strikes  the  buccal  grove  of^  the 
lower  first  molar.  This,  then,  discloses  a  bilateral  normal  mesio-distal 
occlusion  of  the  arches,  and  the  malocclusion  consequently  falls  into 
Class  I.  For  this  illustration  a  case  where  the  upper  incisors  protrude 
has  been  selected,  that  by  comparison  the  student  may  better  grasp 
the  difference  in  the  significance  of  protruding  incisors  in  Class  I  and 
Class  II,  Division  1. 

In  Fig.  77,  the  normal  mesio-distal  relations  of  the  first  molars 
definitely  fixes  the  case  in  Class  I.  Hence  the  protrusion  of  the 
upper  incisors  has  no  significance  in  connection  with  the  classification 
of  the  case. 


MAL0C(^LlISlOM 


m 


In  Fig.  78,  an  examination  of  the  molars  shows  that  the  lower  molar 
on  each  side  is  in  distal  occlusion.  The  mesio-buccal  cusp  of  the  upper 
first  molar  does  not  coincide  with  the  buccal  groove  of  the  lower  first 
molar,  but  on  the  contrary  falls  between  the  mesio-buccal  cusp  of  the 
lower  molar  and  the  buccal  cusp  of  the  second  bicuspid.     The  case 


Fig.  78. — Malocclusion:    Class  II,  Division  1. 


therefore  falls  into  Class  II,  and  since  the  upper  incisors  protrude,  \t 
must  be  in  the  first  division  of  that  class.  Being  bilaterally  distal,  tnth 
the  upper  incisors  protruding,  it  belongs  to  Class  II,  Division  1. 

In  Fig.  79,  we  see  a  case  quite  like  the  last,  and  superficially  like 
Fig.  77,  but  a  study  of  the  molars  shows  a  distal  occlusion  on  one 
side  and  normal  mesio-distal  relations  on  the  other.  And  as  the  upper 
incisors  protrude,  it  is  placed  in  Class  II,  Division  1,  Subdivision. 


Class  II,  Division  1,  Subdivision. 


It  is  in  Class  II,  because  there  is  a  distal  occlusion;  it  is  m  Division 
1,  because  the  upper  incisors  protrude.  It  is  a  Subdivision  because 
the  distal  occlusion  is  confined  to  one  side.  It  is  therefore  unilaterally 
distal  with  protruding  upper  incisors.  i        ,     •  rru 

In  Fig.  80,  we  find  both  lower  first  molars  in  distal  occlusion,     ihe 


124 


MALOCCLUSION  OF  THE  TEETH 


case  therefore  belongs  to  Class  II,  which  includes  all  distal  occlusions. 
We  note  that  the  upper  central  incisors  retrude,  for  which  reason  the 
case  belongs  to  Division  2.  It  is  therefore  a  case  belonging  to  Class  II, 
Division  2,  because  it  is  bilaterally  distal  with  upper  incisors  retruding. 
In  Fig.  81,  we  see  a  case  strikingly  like  the  last,  except  that  on  close 
examination  we  find  that  the  distal  occlusion  is  confined  to  one  side. 


Malocclusion:    Class  II,  Division  2. 


for  which  reason  it  must  be  a  subdivision  case.  It  belongs,  therefore, 
to  Class  II,  Division  2,  Subdivision,  being  unilaterally  distal  with 
retruding  upper  incisors. 

In  Fig.  82,  we  find  the  lower  first  molars  mesial  to  normal.  Indeed, 
they  are  so  far  mesial  that  they  have  lost  all  occlusal  contact  with  the 
upper  first  molars,  so  that  the  classification  is  very  simple.     The  case 


Fig.  81. — Malocclusion:    Class  II,  Division  2,  Subdi^dsion. 

must  belong  to  Class  III,  which  includes  all  mesial  occlusions.  An 
extreme  case  has  been  selected  for  this  illustration,  but  the  actual 
normal  mesio-distal  relations  must  always  be  in  the  mind  as  a  mental 
picture  with  which  the  case  in  hand  may  be  compared,  and  in  the 
presence  of  the  full  complement  of  permanent  teeth,  if  the  lower 
molar  is  found  to  be  mesial  to  normal,  the  case  belongs  to  Class  III. 


MALOCCLUSION 


125 


Observe,  however,  the  qualification  "  in  the  presence  of  the  full  com- 
plement of  the  permanent  teeth."  The  premature  loss  of  a  temporary 
molar,  or  the  extraction  of  a  bicuspid  may  permit  a  lower  first  molar 
to  drift  abnormally  forward,  presenting  a  confusing  picture.  It  is 
always  to  be  remembered,  therefore,  that  this  entire  classification  is 


Fig.  82. — Malocclusion:    Class  III. 

dependent  upon  the  presence,  or  space  for  the  eruption  of,  all  the  per- 
manent teeth,  and  the  drifting  of  teeth  due  to  extractions  or  loss  of 
temporary  teeth  is  always  a  matter  for  separate  consideration. 

In  Fig.  83,  we  find  a  mesial  occlusion  on  one  side,  and  a  normal 
mesiodistal  relation  on  the  other,  for  which  reason  the  case  belongs 
to  Class  III,  subdivision. 


Fig.  83. — Malocclusion:    Class  III,  Subdivision. 

So  much  then  for  the  classification  or  diagnosis  of  cases  in  which 
the  first  permanent  molars  are  present.  It  is  more  than  likely,  how- 
ever, that  many  cases  will  be  seen  before  these  molars  are  erupted  or 
after  they  have  been  badly  mutilated  or  even  lost  through  the  ravages 
of  decay.     For  this  reason  it  is  well  to  note  that  the  occlusion  of 


126  MALOCCLUSION  OF  THE  TEETH 

the  second  deciduous  molars  closely  simulates  that  of  the  first  per- 
manent molars  and  consequently  these  teeth  may  be  used  as  guides 
for  classification.  It  has  also  been  mentioned  that  the  permanent 
cuspids  are  quite  staple  landmarks  and  are  useful  as  guides  to  the 
occlusal  conditions.  At  times  the  bicuspids  may  be  all  the  individual 
has  to  offer  from  which  to  classify  an  abnormality.  Hence  the  student 
can  clearly  see  that  an  intimate  knowledge  of  the  normal  relation  of 
every  tooth  is  absolutely  necessary  if  an  intelligent  grasp  of  the 
abnormal  is  to  be  expected. 

Etiology  of  Malocclusion. — One  might  write  at  great  length  upon 
the  etiology  of  malocclusion  without  at  all  exhausting  the  subject. 
In  this  particular  work  it  does  not  seem  essential  to  discuss  all  the 
theories  of  all  the  theorists.  The  aim  will  be  rather  to  disclose  those 
facts,  the  knowledge  of  which  will  enable  the  hygienist  to  fulfill  her 
avowed  purpose  of  calling  attention  to,  and  so  far  as  possible  abating, 
those  acts  or  causes  which  might  bring  about  or  aggravate  malocclu- 
sion. 

The  factors  involved  as  causative  agents  of  malocclusion  may  be 
divided  into  the  proved  and  the  unproved.  As  examples  of  the 
unproved  theories  in  relation  to  the  causes  of  malocclusion,  enlarge- 
ment of  the  tonsils,  nasal  obstruction,  mouth-breathing  and  adenoids 
may  be  mentioned.  Whether  these  maladies  do  or  do  not  contribute 
toward  malocclusion,  they  are  evidences  of  a  reduced  vitality,  and  as 
diseased  conditions,  should  promptly  be  corrected. 

We  are  told  that  mouth-breathing  causes  malocclusions,  and  that 
adenoids  cause  mouth-breathing.  Conversely,  however,  certain  good 
rhinologists  hold  that  mouth-breathing  induces  adenoids,  due  to  the 
fact  that  the  inhaled  air,  normally  passing  through  the  nares  pro- 
duces a  tonic  effect  upon  the  upper  pharynx,  whereas  when  taken 
through  the  mouth  and  thus  more  directly  into  the  lungs,  the  area 
usually  occupied  by  the  adenoid  vegetations  misses  this  tonicity  sup- 
plied by  the  air,  and  the  hypertrophies  are  induced.  An  ordinary 
rhinitis,  or  head  cold,  especially  during  early  infancy,  by  occluding 
the  nasal  air  passages,  forces  the  child  to  breathe  through  the  mouth. 
If  the  rhinitis  be  long  neglected,  the  mouth-breathing,  which  begins 
as  a  temporary  necessity,  may  become  a  permanent  habit.  The 
theory  at  least  sounds  plausible  enough.  Consequently  a  hygienist 
who  notices  any  conditions  of  this  character,  where  her  charges  may  be 
suffering  with  a  head  cold  of  long  standing,  should  at  once  warn  the 
parent  or  guardians  of  the  possible  ill-results.  Far  better  would  it 
be  for  the  child  to  lose  a  few  days'  schooling  while  being  kept  in  bed  to 
cure  a  cold,  than  that  the  habit  of  mouth-breathing  should  become 
fixed. 

Among  the  proved  causes  of  malocclusion  we  may  enumerate: 

(a)  The  premature  loss  of  deciduous  teeth. 

(b)  Extraction  of  permanent  teeth, 

(c)  Pernicious  habits,  and 

(d)  Lack  of  use. 


MALOCCLUSION  127 

There  are  other  known  causes  which  may  be  found  in  text-books, 
but  those  mentioned  are  of  special  interest  to  the  hygienist. 

(a)  The  Premature  Loss  of  TJecidtious  Teeth. — The  loss  or  extraction 
of  a  deciduous  tooth,  especially  of  the  cuspids  or  any  one  of  the  buccal 
teeth,  will  almost  inevitably  produce  a  pernicious  effect  upon  the  per- 
manent teeth.  The  space  made  by  the  loss  of  the  temporary  tooth 
almost  invariably  closes,  in  part  or  entirely,  so  that  the  opening 
needed  for  the  oncoming  teeth  in  that  locality  is  reduced  in  proportion. 

Why  the  Sjjace  Closes. — In  the  examination  of  a  three-year-old  arch, 
one  wonders  where  the  three  large  permanent  molars  will  find  space 
for  eruption.  This  space,  of  course,  must  be  provided  by  a  growth 
of  the  maxilla  and  mandible  distal  to  the  deciduous  teeth,  distal 
therefore  to  the  last  deciduous  molar.  This  growth  is  coincident  with 
(if  not  actually  caused  by)  the  development  and  eruption  of  the  per- 
manent molars.  The  result  is  a  forward  or  horizontal  movement  of 
the  whole  temporary  arch.  Let  us  study  it  in  detail.  To  make  room 
for  the  arriving  first  permanent  molar,  the  temporary  second  molar 
must  move  forward.  To  accommodate  this  movement  the  first  tem- 
porary molar  must  move  forward,  and  so  on  around  the  arch,  each 
tooth  giving  way  as  the  tooth  behind  it  advances.  Let  us  suppose, 
however,  that  one  of  the  temporary  molars  has  been  lost.  A  space  is 
thus  produced  so  that  the  first  permanent  molar  may  erupt  without 
influencing  the  forward  movement  of  any  of  the  teeth  anterior  to  the 
tooth  extracted.  Indeed,  through  lip  pressure  the  space  may  even 
allow  the  anterior  teeth  to  be  forced  backward.  In  this  way,  by 
closing  of  the  space  while  the  underlying  bicuspid  is  yet  deep  in  the 
bone,  the  bicuspid  may  be  completely  shut  out  of  the  arch,  so  that  it 
either  remains  impacted,  or  else  must  erupt  buccally  or  lingually  of 
normal. 

(6)  Extraction  of  Permanent  Teeth. — ^The  loss  of  any  permanent 
tooth  breaks  up  the  continuity  of  the  arch  and  destroys  the  occlusion. 
It  directly  effects  no  less  than  five  teeth.  The  two  adjacent  teeth 
losing  the  support  of  the  extracted  member,  are  often  forced  to  drift 
or  tip  toward  one  another.  This  tipping  and  drifting  is  more  likely 
to  be  extensive  when  the  extraction  occurs  prior  to  the  eruption  of 
the  second  molars,  as  the  eruption  of  these  distal  teeth  induces  a 
disarrangement  of  the  teeth  distal  to  such  spaces.  This  tipping  of 
the  teeth  interferes  with  the  normal  cusp  interdigitation  of  these  two 
teeth  with  the  three  antagonists  of  the  opposite  jaw.  Thus,  as  has 
been  said,  the  loss  of  one  permanent  tooth  may  directly  spoil  the 
occlusion  of  five  others.  Hence,  of  course,  all  permanent  teeth  which 
can  be  kept  in  a  state  of  health,  should  be  preserved  when  in  normal 
position,  and  when  out  of  position  should  be  brought  to  normal 
occlusion,  if  possible. 

(c)  Pernicious  Habits. — In  regard  to  habits,  perhaps  the  most  com- 
mon is  sucking  the  thumb.  This  phrase,  "sucking  the  thumb,"  is 
met  throughout  the  entire  literature,  and  is  particularly  supposed  to 


128  MALOCCLUSION  OF  THE  TEETH 

induce  protrusion  of  the  upper  anterior  teeth.  But  the  thumb  is  not 
always  in  the  mouth  in  such  a  way  as  to  produce  this  effect,  nor  is  it 
always  the  thumb  which  the  child  introduces  into  the  mouth. 
Recently  a  casual  glance  into  the  mouth  of  a  baby  girl  patient  of  four, 
disclosed  what  seemed  to  be  a  protrusion  of  the  upper  incisors.  The 
mother  was  asked,  "Does  this  child  suck  her  thumb?"  Like  a  flash 
the  child  replied,  "No,  I  suck  two  fingers;  want  to  see  me?"  and  she 
proceeded  to  give  a  demonstration.  She  placed  just  two  fingers  of 
her  right  hand  in  her  mouth,  the  finger-tips  curled  downward  under 
her  tongue.  In  this  manner  it  would  seem  that  the  weight  of  her  arm 
had  held  the  mandible  downward  and  backward,  so  that  a  marked 
example  of  Class  II,  Division  1,  had  been  produced,  although  none 
of  the  temporary  teeth  had  yet  been  shed.  The  apparent  protru- 
sion of  the  upper  teeth  was  no  real  protrusion  at  all.  As  the  child 
was  not  a  sufferer  from  adenoids,  had  no  nasal  obstruction  of  any  sort, 
had  never  been  a  mouth-breather,  and  was  the  picture  of  health,  it 
is  reasonable  to  attribute  the  deformity  of  the  jaws  in  her  case  to  this 
peculiar  method  of  sucking  the  fingers.  The  thumb  is  also  sometimes 
introduced  into  the  mouth  in  the  same  manner,  and  not  always  with 
the  ball  of  the  thumb  against  the  upper  teeth. 

Other  baneful  habits  are  sucking  the  lips  or  the  tongue,  or  habit- 
ually resting  the  tongue  between  the  incisors,  not  forgetting  the 
abominable  practice  of  nursemaids,  and  some  mothers,  of  giving  the 
baby  a  "pacifier"  or  "comforter." 

These  habits  are  particularly  mentioned  here  because  it  seems  prob- 
able that  in  the  near  future  the  sphere  of  the  dental  hygienist  will  be  so 
broadened  that  she  will  enter  the  homes  of  many  children  long  before 
they  arrive  at  the  school  age,  in  which  case  an  important  part  of  her 
duty  would  be  to  look  for,  and  warn  mothers  against,  these  habits. 

{d)  Lack  of  Use. — ^This  brings  us  to  a  consideration  of  a  lack  of 
use.  It  is  a  commonly  accepted  physiological  law  that  the  use  of 
any  organ,  or  part  of  the  body,  contributes  toward  its  development. 
Normal  use  results  in  normal  development,  where  not  hindered  by 
other  agencies.  Abnormal  or  immoderate  use  may  cause  an  over- 
growth, as  we  see  in  the  muscles  of  athletes;  while  disuse  results  in 
underdevelopment  or  even  atrophy. 

The  Growth  of  the  Jaws. — If  we  examine  the  normal  child  denture 
at  the  age  of  three  or  four,  we  observe  twenty  teeth  symmetrically 
arranged  about  the  arches  and  completely  filling  them.  When  we 
remember  that  these  twenty  deciduous  teeth  will  be  succeeded  by 
twenty  permanent  teeth  considerably  larger  in  size,  we  recognize  that 
if  the  latter  are  to  erupt  in  normal  occlusion,  the  bones  of  the  arches 
must  become  enlarged,  or  in  other  words,  there  must  be  a  growth 
increasing  the  circumference  of  the  arches.  Since  the  growth  of  the 
temporary  teeth  themselves  is  aheady  complete,  a  growth  of  their 
bony  supports  must  result  in  producing  spaces  between  these  teeth. 
We  see  this  beautifully  shown  in  Fig.  84,  which  illustrates  the  upper. 


MALOCCLUSION  129 

and  lower  arches  of  a  boy  of  four  and  a  half  years  of  age.  We  have  but 
to  glance  at  such  a  set  of  deciduous  teeth  to  see  how  admirably  Nature, 
when  unhindered,  will  provide  for  all  emergencies.  We  easily  compre- 
hend that,  by  growth,  space  is  being  provided  against  the  advent  of 
a  set  of  larger  teeth. 

But  what  shall  we  think  of  such  a  set  of  teeth  as  is  shown  in  Fig. 
85?     This  child  was  five  years  of  age,  six  months  the  senior  of  the 


Normal  growth  of  dental  arches.     Aged  four  and  a  half  years. 


other  child,  yet  we  find  no  spaces  between  the  teeth  and  consequently 
no  growth  of  the  alveolar  bone.  We  must  wonder  then,  "Where  will 
the  permanent  teeth  erupt?"  They  certainly  cannot  appear  in  proper 
alignment  with  such  a  lack  of  space.  These  two  models  then  illustrate 
well  the  contrast  in  appearance  of  a  normally  developing  deciduous 
denture  with  one  that  is  failing  to  take  on  proper  growth. 

It  is  but  natural  to  believe  that  this  development  of  the  bones 
about  the  deciduous  teeth  is  largely  dependent  upon  the  extent  and 
nature  of  the  use  or  disuse  of  the  teeth. 


s 

^H 

5 

9H 

1 

p^^^^l 

^^B^  '       't^^^^H 

^r^P 

B? 

'  ^^1 

r  1 

1 

jl 

Fig.  85. — Undeveloped  dental  arches.     Aged  five  years. 

The  normal  use  of  the  teeth  would  necessitate  the  thorough  masti- 
cation of  food;  food  thus  masticated  would  be  properly  insalivated, 
and  hence  properly  prepared  for  its  reception  by  the  stomach.  With 
all  the  organs  of  digestion  in  a  state  of  health,  the  result  would  be  the 
thorough  assimilation  of  the  food,  a  correct  metabolism,  and  hence 
a  proper  share  of  the  nourishment  would  finally  reach  the  jaw  bones. 


130  MALOCCLUSION  OF  THE  TEETH 

so  that  the  thoroughness  of  the  work  done  by  the  dental  organs  would 
bring  its  own  repayment  in  the  normal  share  of  pabulum  brought  to 
the  alveolar  environments  of  the  teeth.  In  this  manner  a  normal 
physiological  cycle  would  be  established,  and  of  course  any  disuse  of 
the  teeth  would  proportionately  cause  a  disarrangement  of  this  cycle. 

While  it  is  well  to  bear  these  facts  in  mind,  yet  there  is  another 
aspect  of  use  and  disuse  of  the  dental  organs  to  which  attention  must 
here  be  called.  Entirely  aside  from  any  interference  with  the  proper 
nourishing  of  the  body  and  of  the  jaw  bones,  the  use  or  disuse  of  the 
teeth  directly  affects  the  growth  and  development  of  the  maxilla  and 
mandible,  through  the  muscular  and  mechanical  forces  of  mastication. 
Indeed  it  is  claimed  that  not  only  the  bones  of  the  jaws,  but  the 
entire  cranium  may  be  thus  affected.  To  emphasize  this  fact,  a  lib- 
eral quotation  is  made  from  an  article  by  Dr.  Lawrence  W.  Baker, 
published  in  Items  of  Interest,  February,  1911. 

"Among  the  first  voluntary  coordinate  muscular  actions  of  a  human 
being  after  coming  into  the  world  is  that  made  with  the  muscles  of 
mastication  in  taking  food  to  sustain  life.  Long  before  the  infant 
can  hold  up  its  head,  or  has  gained  control  over  those  useful  organs, 
the  hands,  the  muscles  of  mastication  are  highly  developed  and  are 
used  with  great  vigor. 

"During  the  act  of  nursing,  the  action  of  this  set  of  muscles  is  so 
vigorous  that  it  demands  an  increased  blood  supply,  to  the  extent 
that  the  heart's  action  is  greatly  increased;  the  excessive  flow  of  blood 
to  these  parts  is  indicated  by  a  reddening  of  the  whole  head,  and  the 
fontanelles  themselves  are  caused  to  pulsate  so  that  the  untrained 
observers  comment  on  their  movement. 

"Later,  with  the  advent  of  the  dental  equipment,  this  group  of 
muscles  is  given  more  leverage,  and  its  action  becomes  consequently 
more  powerful;  in  fact,  the  force  exerted  on  the  bones  of  the  head 
from  the  pull  of  these  muscles  during  life  is  tremendous  and  amounts 
to  many  hundreds  of  thousands  of  tons  of  force.  I  have  long  been 
convinced  that  this  great  force  on  the  skull,  and  the  great  flow  of 
arterial  blood  to  the  head  caused  by  this  muscular  activity,  is  a  pow- 
erful influence  in  the  development  of  the  bones  of  the  head  and  the 
important  organs  incased  therein. 

"It  occurred  to  me  that  if  the  hypothesis  regarding  the  influence 
of  the  dental  equipment  on  the  formation  of  the  bones  of  the  head  were 
correct,  interference  with  the  laws  of  occlusion  in  the  lower  animals 
would  show  consequent  effect  in  the  formation  of  the  bones  of  the 
skull;  and  if  variation  occurred  it  might  throw  some  light  on  the 
most  complex  problem  of  the  development  of  the  human  head. 

"To  test  the  theory  the  following  experiment  was  performed:  A 
litter  of  four  rabbits  was  selected  at  the  age  of  weaning.  Two  of  the 
animals  were  operated  on  by  grinding  down  all  the  teeth  on  the  right 
side  of  the  lower  jaw  and  the  superior  right  central  incisor.  As  the 
teeth  elongated,  repeated  grinding  rendered  them  useless,  so  that 


MALOCCLUSION 


131 


all  the  mastication  was  performed  on  the  left  side.    The  fourth  rabbit 
was  kept  in  the  normal  state  for  a  standard  of  comparison. 

"After  seven  months,  the  skeleton  of  one  of  the  rabbits  was  pro- 
cured and  the  skull  was  found  to  vary  as  shown  in  Fig.  86,  which  is  a 
photograph  of  its  upper  aspect.  It  will  be  noted  by  the  drawn  lines 
that  there  is  a  deviation  of  the  bones  to  the  left.  (Right  and  left  in 
this  description  refers  to  the  right  and  left  side  of  the  animal.)  The 
suture  between  the  parietal  and  frontal  bones  does  not  run  strictly 
at  right  angles  to  the  longitudinal  axis  of  the  skull;  the  right  frontal 
bone  projects  farther  forward  than  the  left  one.  It  will  also  be 
observed  that  the  left  zygomatic  space  is  longer  and  more  advanced 
than  the  right  space.  The  most  noticeable  deviation  is  in  the  nasal 
bones,  both  bones  being  twisted  to  the  left. 


Fig.  86. — The  upper  aspect  of  the 
skull  of  a  rabbit  operated  on.  Observe 
the  unequal  development  of  each 
lateral  half  of  the  skull. 


Fig.  87. — Lower  aspect  of  Fig 


"On  the  lower  aspect  of  the  skull.  Fig.  87,  it  will  be  seen  that  the 
deviation  extends  throughout  the  entire  skull.  The  most  remarkable 
deviation  is  that  the  anterior  root  of  the  right  zygomatic  arch  (the 
zygomatic  process  of  the  maxillary  bone)  is  retreated  while  the  body 
of  the  right  maxillary  bone  itself  with  the  teeth  that  it  contained  is 
greatly  advanced. 

"The  results  of  this  experiment  seem  remarkable  to  me. 

"Who  would  have  thought  that  by  interfering  with  the  laws  of 
occlusion  the  skull  would  have  decreased  in  weight,  and  that  every 


132 


MALOCCLUSION  OF  THE  TEETH 


suture  and  every  bone  in  the  head  would  have  varied  as  we  have  seen? 
This  experiment  strongly  indicates  how  important  is  the  masticatory 
equipment  of  man  to  the  development  of  the  head,  and  it  also  brings 
fresh  illustrations  of  the  importance  of  the  sadly  neglected  temporary 
dentition  which  serves  during  the  important  developmental  period 
of  childhood." 

The  previous  quotation  gives  in  full  the  details  of  Dr.  Baker's 
experiment,  and  his  findings  in  one  case.  His  examination  of  the 
second  rabbit  upon  which  he  experimented  disclosed  exactly  similar 
variations  from  the  normal,  whereas  the  control  animal  was  practi- 
cally symmetrical.^  Until  future  experimenters  prove  these  deductions 
to  be  erroneous,  we  may  agree  with  Dr.  Baker  that  the  disuse  of  the 
teeth  may  result  in  extreme  interference  with  the  development,  not 
alone  of  the  jaws,  but  of  contiguous  parts  of  the  cranium. 


Caries  of  teeth  causing  voluntary  disuse  of  the  teeth. 


Reasons  for  Lack  of  Use. — Disuse  of  the  dental  organs  may  be  either 
involuntary  or  voluntary.  It  is  involuntary  when  the  habits  of  masti- 
cation are  hasty,  or  where  the  food  used  is  of  such  a  character  that 
heavy  mastication  is  not  necessary.  "What  an  injustice,  then,  is  done 
to  children  who  are  fed  upon  gruels,  sloppy  food  and  other  articles  of 
diet  which  require  little  or  no  masticatory  effort  to  reduce  them  to  a 
consistency  readily  swallowed? 

The  voluntary  disuse  of  the  teeth  is  the  direct  result  of  caries  which 
renders  the  chewing  of  food  so  difficult,  or  so  painful,  that  the  child 
elects  either  to  swallow  its  food  unchewed,  or  else  to  select  food  that 
needs  no  masticatory  effort. 

In  Fig.  88,  we  see  the  right  and  left  sides  of  the  occluded  models  of 
a  child  four  years  of  age.     On  the  left  side  of  the  mouth  caries  has 

1  Dr.  Baker  has  continued  his  experiments,  and  has  had  exactly  similar  results  with 
animals  other  than  rabbits.  See  his  report  thereon,  Dental  Items  of  Interest,  July, 
1916. 


MALOCCLUSION  133 

destroyed  the  little  molars  and  cuspids  almost  to  the  gum  line.  We 
cannot  look  upon  this  picture  without  thinking  of  the  rabbits,  whose 
teeth  Dr.  Baker  filed  or  ground  away  to  prevent  mastication  on  one 
side.  When  we  recall  the  results  of  the  experiment  with  the  rabbits, 
we  begin  to  appreciate  the  seriousness  of  such  conditions  in  a  human 
young  one,  during  the  most  stressful  periods  of  development.  The 
word  stressful  is  used  because,  whereas  an  adult  needs  only  to  restore 
the  tissues  of  his  body  which  are  lost  by  use,  a  child  must  likewise  do 
this  and  at  the  same  time  obtain  and  assimilate  sufficient  food  with 
which  to  increase  his  weight  and  stature.  How  can  he  do  this  handi- 
capped with  a  masticating  apparatus  so  destroyed?  In  the  experi- 
ment with  the  rabbit,  Dr.  Baker  left  the  little  animal  with  one  side  of 
his  masticating  apparatus  perfect,  so  that  perhaps  he  might  properly 
masticate  sufficient  food  for  the  proper  nourishment  of  his  body. 
It  is  this  fact  that  made  Dr.  Baker's  results  so  significant.  There  is 
every  reason  to  believe  that  the  rabbits  operated  upon  ate  just  as 
much  food  as  the  control  animal,  so  that  the  divergencies  from  normal 
found  in  the  skulls  were  not  attributable  to  lack  of  nourishment,  but 
to  lack  of  use  of  one  side  of  the  jaws. 


Fig.  89. — Same  case  as  Fig.  88,  occlusal  view.  - 

The  child  whose  models  are  shown  fared  not  so  well  as  Dr.  Baker's 
rabbits,  because  on  both  sides  occlusion  was  extensively  interfered 
with.  The  cavities  in  the  teeth  are  so  large  that  a  considerable  por- 
tion of  their  occlusal  areas  has  been  lost,  and  the  approximal  con- 
tacts likewise  having  been  destroyed,  the  protection  of  the  interprox- 
imal septa  has  disappeared,  so  that  food  readily  packs  upon  these 
easily  injured  and  sensitive  tissues,  with  the  result  that  mastication 
becomes  painful,  and  the  child  voluntarily  declines  to  use  his  teeth. 

Fig.  89  shows  the  occlusal  view  of  these  two  jaws,  and  the  extent 
to  which  caries  has  destroyed  the  occlusal  contactual  area  is  disclosed. 
Comparing  these  models  with  those  shown  in  Fig.  84  we  note  the 
lack  of  development. 

At  this  point  it  may  be  well  to  consider  again  the  models  shown  in 
Fig.  85.  These  likewise  show  lack  of  development  of  the  arches,  yet 
the  teeth  themselves  are  not  affected  by  caries,  so  the  child  could 


134  MALOCCLUSION  OF  THE  TEETH 

have  used  them  perfectly;  therefore  it  is  not  to  be  claimed  that  disuse 
is  the  sole  cause  of  lack  of  development.  It  may  be  the  chief  cause 
in  some  instances  and  only  one  of  several  factors  in  others.  In  the 
case  of  the  child  whose  models  are  shown  in  Fig.  85,  the  physical 
history  is  not  known.  It  will  suffice  for  present  purposes  to  consider 
two  possible  hypotheses.     While  this  child  cannot  have  suffered  from 


Fig.  90. — Malocclusion  due  to  lack  of  use. 

voluntary  disuse  of  the  dental  organs,  since  the  teeth  are  all  sound 
there  may  have  been  involuntary  disuse  due  to  the  soft  nature  of  his 
food.  Again,  considering  the  perfectness  of  the  teeth,  this  may  not 
be  a  case  of  lack  of  development  at  all.  There  is  no  definite  age  at 
which  a  particular  development  of  the  jaws  must  occur.  We  cannot 
say  certainly  that  the  first  permanent  molars  will  erupt  at  a  stated 


Same  case  as  Fig.  90,  occlusal  view. 


age,  the  incisors  at  another,  the  cuspids  at  another.  The  writer  has 
seen  a  complete  denture  of  thirty-two  teeth  at  the  age  of  fourteen, 
and  in  another  case,  the  upper  cuspids  arriving  as  late  as  the  nine- 
teenth year,  in  which  case  all  the  previously  erupted  teeth  had  likewise 
appeared  long  after  what  is  supposed  to  be  the  normal  time  of  erup- 
tion.    Looking  at  a  child  denture  prior  to  the  eruption  of  the  first 


M  A  LOCCL  USION  1 35 

permanent  molars,  if  we  note  growth  spaces,  as  seen  in  Fig.  84,  we 
may  say  that  normal  development  is  present,  but  in  the  absence  of 
such  growth  spaces,  as  in  Fig.  85,  we  cannot  positively  decide.  It 
may  be  a  case  of  lack  of  development  (as  a  mere  illustration  of  which 
the  models  are  used),  or  it  may  be  a  case  of  slow  or  tardy  development. 
As  examples  of  a  period  slightly  later  than  that  shown  in  Ings.  88 
and  89,  Figs.  90  and  91  are  introduced.  This  child's  mouth  was 
first  examined  prior  to  the  appearance  of  the  permanent  molars.  Not 
a  tooth  in  the  two  arches  was  free  from  caries.  The  upper  incisors  were 
barely  showing  above  the  gum  line,  and  all  four  were  abscessed,  for 
which  reason  they  were  extracted,  as  were  three  or  four  others.  Com- 
plete lack  of  occlusion  existed.  The  child  was  undersized,  anemic  and 
of  a  generally  degenerate  appearance.  Her  father  was  a  physician, 
however,  and  after  removal  of  the  abscessed  teeth  he  w^as  advised  to 
feed  the  child  on  food  that  would  yield  as  much  nourishment  as  possible. 
It  was  impossible  to  obtain  models  of  her  mouth;  it  would  have  been 
cruel  to  try.  When  next  she  was  seen,  two  years  later,  the  models  here 
illustrated  were  made.  Even  with  the  eruption  of  the  first  molars,  the 
masticating  possibilities  have  not  been  greatly  improved,  as  they 
decayed  almost  as  fast  as  they  appeared,  so  it  was  said.  However 
that  may  be,  we  have  here  a  marked  case  of  prolonged  lack  of  use  and 
malnutrition  and  cannot  be  surprised  at  the  resultant  malocclusion. 
On  one  side  we  note  that  the  lower  molar  is  in  distal  occlusion.  On 
the  other  side  the  occlusion  of  the  molars  is  apparently  normal,  but 
there  is  little  reason  to  doubt  that  the  low^r  molar  has  drifted  forward 
because  of  the  premature  loss  of  the  two  temporary  teeth.  In  any 
event  it  is  a  marked  example  of  malocclusion  due  to  lack  of  use  follow- 
ing the  ravages  of  caries  in  the  temporary  set,  so  that  from  this  case 
alone  we  may  gain  some  cognizance  of  the  possible  evils  of  dental 
disease  which  might  have  been  prevented  to  a  great  degree  by  proper 
attention  to  mouth  hygiene. 


CHAPTER  V. 
INFLAMMATION. 

By  LeROY  M.  S.  MINER,  M.D.,  D.M.D. 

Inflammation  may  well  be  called  the  cornerstone  of  Pathology, 
for  an  accurate  conception  of  the  principles  involved  in  the  phenomena 
of  inflammation  is  necessary  in  order  to  have  a  foundation  upon  which 
to  build  a  knowledge  of  general  pathology. 

Inflammation  in  its  various  forms  is  so  exceedingly  common  that 
without  a  knowledge  of  the  changes  that  take  place  one  cannot  hope 
to  understand  the  manifestations  which  occur  in  diseased  conditions. 

Definition. — Inflammation  may  be  described,  in  a  word,  as  a  response 
or  reaction  to  an  irritation  or  injury.     Its  yurpose  is  twofold: 
1..  To  counteract  or  neutralize  the  agent  causing  the  injury. 
2.  To  repair  the  injury  produced. 

Thus  it  is  seen  that  inflammation  is  intended  to  be  a  building  up  pro- 
cess; a  beneficial  effort  of  Nature  to  repair  damage.  Unfortunately 
it  not  infrequently  happens  that  under  unfavorable  conditions  it 
becomes  distinctly  destructive  instead  of  reparative. 

Classification. — The  many  types  of  inflammation  have  been  classi- 
fied in  various  ways.  The  terms  most  frequently  used,  however,  are 
(1)  acute  and  (2)  chronic. 

It  may  also  be  classified  according  to  the  location.  Catarrhal 
inflammation  affects  the  epithelial  structures,  especially  the  mucous 
membranes;  inflammation  is  said  to  be  Interstitial,  when  the  connec- 
tive or  supporting  tissues  are  involved;  or  Parenchymatous,  when 
the  functionating  cells  of  an  organ  are  attacked. 

Inflammation  has  also  been  described  as  Ulcerative,  when  there  is 
loss  of  tissue  by  necrosis  or  gangrene;  Exudative,  when  the  process 
is  characterized  by  unusual  exudates  as  in  pleuritic  effusion;  Sup- 
purative, when  the  inflammation  ends  in  suppuration  or  the  formation 
of  pus. 

While  these  classifications  help  to  describe  the  location  or  the  type 
of  inflammation,  and  while  the  clinical  aspects  may  vary  somewhat, 
it  must  be  firmly  borne  in  mind  that  the  phenomena  of  the  reactions 
which  take  place  are  essentially  the  same  in  all  forms.  The  location 
of  the  injury  will  determine  to  a  considerable  extent  the  effect,  but 
the  reaction  is  fundamentally  the  same. 

Inasmuch  as  the  circulation  of  both  blood  and  lymph  plays  a  very 
important  role  in  the  phenomena  of  inflammation,  it  is  necessary 
to  have  some  knowledge  of  the  normal  circulation  and  also  some 


TtlE  CONSTITUENTS  OF  THE  NORMAL  BLOOD  137 

idea  of  the  simpler  tissues  which  may  be  affected  before  studying  the 
process  itself. 

The  Normal  Circulation. — The  circulation  of  blood  differs  in  each 
of  the  three  types  of  vessels. 

In  the  arteries,  which  carry  the  fresh  red  blood,  the  flow  is  inter- 
mittent, the  red  blood  corpuscles  flow  in  the  center  of  the  vessel 
(axial  core),  while  between  them  and  the  vessel  wall  is  a  colorless 
zone  called  the  plasma  zone.  The  white  blood  corpuscles  travel  in 
this  zone  and  travel  much  more  slowly  than  the  red  corpuscles. 

In  the  capillaries,  or  the  intermediate  vessels,  the  blood  flow  is 
slow  and  continuous.    There  is  no  plasma  zone. 

The  flow  in  the  veins  is  continuous  and  slower  than  in  the  arteries. 
The  plasma  zone  is  present,  but  less  sharply  defined  than  in  the 
arteries. 

The  Constituents  of  the  Normal  Blood.— The  chief  constituents  of 
the  normal  blood  are  eight  in  number,  as  follows: 
I.  Red  blood  corpuscles,  erythrocytes. 
II.  Blood  platelets. 

III.  Polymorphonuclear  leukocytes  (leukocytes  with  many  nuclei). 

IV.  Endothelial  leukocytes. 
V.  Lymphocytes. 

VI.  Eosinophiles. 
VII.  Mast  cells. 

VIII.  Blood  plasma. 

Groups  III  to  VII  are  various  types  of  white  blood  cells. 

The  red  blood  corpuscles  are  bell-  or  cup-shaped  masses  of  cytoplasm 
containing  no  nucleus.  One  cubic  millimeter  of  blood  under  normal 
conditions  contains  4,500,000  to  5,000,000  red  corpuscles  and  at  birth 
about  6,000,000.  These  corpuscles  are  not  permanent  cells,  but  are 
short-lived.  Their  function  is  the  carrying  of  oxygen,  which  forms  a 
loose  combination  with  hemoglobin,  which  is  the  most  important 
constituent  found  in  the  protoplasm  of  these  cells.  The  red  blood 
corpuscles  are  derived  from  the  erythroblasts  of  the  bone-marrow. 

The  blood  platelets  are  round  or  oval  disks  about  one-half  the  size 
of  the  red  blood  corpuscles.  One  cubic  millimeter  contains  250,000 
to  500,000  platelets. 

The  white  corpuscles  grouped  together  are  present  in  much  smaller 
numbers  than  the  red  blood  corpuscles,  there  being  only  8000  per 
cubic  millimeter  on  the  average.  There  are  about  600  red  to  1  white 
corpuscle. 

The  polymorphonuclear  leukocytes  are  the  most  frequently  found 
white  corpuscles  and  form  70  to  72  per  cent,  of  the  total  number. 
They  are  larger  than  the  red  blood  corpuscles.  Under  the  microscope 
the  nucleus  of  this  cell  attracts  attention.  The  nucleus  is  irregular 
and  has  rounded  lobules.  The  cell  membrane  is  sharply  defined. 
These  cells  are  formed  in  the  bone-marrow  also. 


138  ■  INFLAMMATION 

Endothelial  leucocytes  or  mononuclear  leukocytes  are  larger  even 
than  the  polymorphonuclear  cells,  being  two  or  three  times  as  large 
as  the  red  blood  corpuscles.  In  number  they  make  up  only  2  to  4  per 
cent,  of  all  the  white  cells.  Ihey  are  derived  from  the  endothelial 
cells  lining  the  bloodvessels. 

The  lympJwcytes  are  found  most  frequently  next  to  the  polynuclear 
cells.  They  form  22  to  25  per  cent,  of  all  the  white  corpuscles.  They 
are  about  the  size  of  the  red  corpuscles.  The  appearance  is  charac- 
teristic. The  cells  are  round  and  they  take  the  stain  well,  especially 
the  periphery.  Lymphocytes  are  produced  in  lymphoid  tissue  and 
especially  in  the  lymph  nodes. 

Eosinophiles  make  up  2  to  4  per  cent,  of  the  total  leukocytes.  The 
nucleus  is  frequently  shaped  like  a  horseshoe,  and  the  cell  itself  may 
be  larger  than  the  polynuclear  leukocytes.  It  derives  its  name  from 
the  intense  staining  with  eosin.     They  are  derived  from  bone-mlarrow. 

The  mast  cells  make  up  but  five-tenths  of  1  per  cent.  They  are 
also  derived  from  bone-marrow. 

Blood  plasma  is  the  fluid  part  of  the  blood  and  contains  fibrin, 
which  plays  an  active  part  in  the  phenomena  of  coagulation.  With 
the  fibrin  removed  the  plasma  is  called  serum. 

In  addition  to  this  brief  study  of  the  blood  and  its  circulation  it 
may  be  well  to  mention  some  of  the  basic  histological  structures  which 
are  concerned  in  the  study  of  the  inflammatory  process.  They  are 
as  follows: 

I.  Connective  tissue  (fibroblasts). 
II.  Endothelial  cells. 

III.  Nerves. 

IV.  Lymph  vessels  and  spaces. 
V.  Bloodvessels. 

Connective  Tissue. — The  function  of  this  tissue,  as  the  name  sug- 
gests, is  to  bind  or  support  other  tissue.  The  cell  of  which  it  is  formed 
is  called  the  fibroblast.  These  cells,  as  a  rule,  are  flat,  elongated  cells 
with  oval  nuclei.  The  fibroblast  frequently  plays  an  important  part 
in  inflammatory  processes. 

Endothelial  Cells. — ^These  cells  line  the  blood  and  lymph  vessels. 
In  form  they  are  flattened  and  have  an  oval  nucleus. 
The  inflammatory  process  may  be  divided  into  three  parts: 
I.  The  injurious  agent  or  the  cause. 
11.  The  injury  done  to  the  tissues. 

III.  The  resulting  reaction  to  the  injurious  agent  and  to  the  injury. 
The  Injurious   Agent  or  Cause. — Some  writers  have   classified   the 
causes  of  inflammation  under  two  headings: 

1.  The  predisposing  cause. 

2.  The  exciting  cause. 

As  a  predisposing  cause  of  inflammation  age  may  be  mentioned. 
In  growing  children,  the  nutritional  and  developmental  changes  pre- 
dispose to  inflammation  of  the  mucous  membranes.     The  frequency 


PLATE    IV 


The  Elements  of  Normal  Blood.     (Simon.) 

a,  red  cells  in  rouleaux;  h,  crenated  red  cells;  c,  finely  granular  (neutrophilic)  leuko- 
cytes; d,  coarsely  granular  (eosinophilic)  leukocytes;  e,  small,  and/,  large  mononuclear 
leukocytes;  g,  plaques. 


TUK  INJflU/OllS  A(1I<:NT  ()]i   CAUSE  V.'>\) 

of  stomatitis  in  cliildren  i«  an  exaiiii)ic.  In  old  aj^e  the  loweriiiK  of 
the  resistance  i>re(Hsp()ses  to  the  infianiniations  of  bacterial  orif^in. 
Bronchitis  is  an  example.  Fatigue  and  worry  are  said  to  be  predis- 
posing causes.  Any  condition  that  lowers  the  natural  resistance  may 
be  regarded  as  a  predisposing  cause. 

The  exciting  cavse,  or  the  active  injurious  agents  may  be  di\'ided 
into  three  groups: 

I.  Mechanical:  cuts,  blows,  foreign  bodies. 
II.  Physical:     heat,  cold,   sunlight   (sunburn),  electricity,   .r-ray, 

radium. 
III.  Chemical: 

(a)  Inorganic  compounds:    acids,  alkalies,  poisons. 

(b)  Organic:   microorganisms,  bacteria  and  their  toxins. 
This  last  group,  especially  the  bacteria,  form  the  chief  cause  of 

inflammation.  In  fact,  so  commonly  is  bacterial  invasion  the  cause 
that  it  has  been  incorrectly  assumed  that  inflammation  was  dependent 
upon  bacteria  or  their  products.  As  a  matter  of  fact  the  lesions  pro- 
duced by  the  injurious  agents  other  than  bacteria  are  identical  to 
those  of  bacterial  origin. 

It  is  not  necessary  to  go  into  great  detail  regarding  the  bacteriology 
of  inflammation,  but  some  of  the  more  common  bacteria  may  be  briefly 
described.  The  three  most  common  organisms  are  the  Staphylo- 
coccus pyogenes  aureus,  Streptococcus  pyogenes  and  the  pneumo- 
coccus. 

The  staphylococcus  is  found  on  the  skin,  or  in  the  mouth,  and  is 
very  common.  It  may  possess  little  or  no  virulence,  or  it  may  become 
extremely  pathogenic  when  abnormal  conditions  exist.  It  is  the  most 
frequent  organism  found  in  pus.  It  is  a  small,  round  cell  and  tends 
to  form  in  groups  or  clusters.  When  grown  artificially  it  produces 
a  distinctly  yellowish  color  in  the  medium. 

The  streptococcus  is  a  more  dangerous  organism,  but  it  is  not  so 
common  as  the  staphylococcus.  It  is  not  infrequently  found  in  the 
mouth  and  nose.  It  is  often  found  in  suppurative  conditions  with 
the  staphylococcus.  It  is  a  spherical  organism  which  has  the  char- 
acteristic of  growing  in  chains. 

The  pneumococcus  is  found  frequently  in  inflammatory  conditions. 
It  is  said  to  be  a  normal  inhabitant  of  the  mouth.  Morphologically 
these  organisms  appear  like  elongated  cocci  and  tend  to  grow  in  pairs 
or  short  chains.  Under  some  conditions  a  well-defined  capsule  is  seen. 
This  organism  has  been  found  very  frequently  in  the  inflammatory 
conditions  of  the  alveolar  process,  commonly  known  as  pyorrhea 
alveolaris.  The  Bacillus  pyocyaneus,  typhoid  bacfllus,  colon  bacillus 
and  tubercle  bacillus  are  other  notable  examples  of  pathogenic  bacteria 
which  produce  their  more  or  less  characteristic  inflammations. 

The  action  of  an  injurious  agent  may  be  severe  or  slight,  brief  or 
prolonged.  The  eft'ect  varies  accordingly.  Some  agents  produce  a 
lesion  very  quickly,  others  only  after  acting  over  a  long  period  of 


140  INFLAMMATION 

time.  The  action  may  be  local  or  general:  local,  as  in  the  case  of  a 
blow;  general,  as  in  the  case  of  diphtheria  toxin. 

The  Injury. —  Definitions. — Injury  is  the  term  applied  to  the  changes 
produced  in  tissues  and  organs  by  harmful  agents. 

Lesion  is  the  term  applied  to  any  structural  change  in  tissues  and 
organs,   no  matter  how  produced. 

Necrosis  means  death  and  may  be  used  to  indicate  death  of  any 
tissue,  or  of  a  single  cell. 

It  is  possible  for  injury  to  have  been  done  without  being  able  to 
demonstrate  it.  In  tetanus  and  rabies  it  may  be  impossible  to  demon- 
strate any  morphological  change,  even  though  the  reaction  is  most 
violent.  Thus  it  is  seen  that  inflammation  is  not  necessarily  a  local 
reaction. 

The  Reaction. — ^The  reaction  to  an  injurious  agent  is  the  most  inter- 
esting. This  reaction  naturally  varies  very  considerably,  and  this 
depends  on  the  amount  and  nature  of  the  injurious  agent  and  on  the 
severity  of  the  injury.     It  may  be  evidenced  in  three  ways: 

I.  By  chemical  changes,  as  alteration  in  secretion  or  excretion. 
II.  By  morphological  changes,  as  the  presence  of  serum,  fibrin  and 

proliferated  cells. 

III.  Physiologically,  by  alteration  in  functional  activity. 

As  already  stated,  the  object  of  the  reaction  is  to  get  (a)  rid  of  the 
injurious  agent,  if  it  is  still  present;  (b)  to  neutralize  its  action;  and 
(c)  to  repair  the  injury  which  has  taken  place. 

The  chemical  and  physiological  changes  are  usually  less  prominent 
than  the  morphological  changes.  The  changes  in  the  blood  following 
poisoning  by  illuminating  gas  is  a  good  example  of  the  chemical  change. 
The  convulsions  produced  in  poisoning  by  strychnine  illustrate  the 
physiological  changes. 

Inasmuch  as  the  morphological  changes  are  most  frequently  seen 
and  have  been  the  most  thoroughly  studied,  this  phase  of  the  subject 
can  be  studied  to  advantage. 

The  morphological  changes  (which  are  partly  chemical)  which  take 
place  in  tissues  following  an  injury  are  as  follows: 
I.  Circulatory  disturbances. 

II.  Inflammatory  exudation. 

The  Circulatory  Disturbances. — ^These  occur  in  the  following  order: 

1.  A  momentary  spasm  in  the  bloodvessels,  when  the  irritant 
flrst  acts. 

2.  Dilatation  of  the  vessels  with  a  more  rapid  flow. 

3.  The  vessels  still  further  dilate  and  become  engorged,  but  the 
flow  decreases,  and  may  even  stop  in  some  of  the  capillaries  and  veins. 
The  leukocytes  become  attached  to  the  walls  of  the  veins. 

4.  The  transmigration  of  the  leukocytes. 

These  cells,  especially  the  polynuclear  form,  have  been  called  the 
soldiers  of  the  blood,  for  they  rush  to  the  seat  of  injury  and  slowly 
but  surely  pass  through  the  vessel  wall  into  the  tissues  (ameboid  move- 


PLATE  V 


a  b  b' 


• 


• '  • 


'■m^' 


f 


f 


a,  macrolymphoblast ;  b,  microlymphocyte;  b',  older  form;  b",  monocytoid  form ; 
c,  macrolymphoidocytes ;  c',  monocytoid  forms;  d,  microlymphoidocytes;  e,  Rieder 
forms  of  macrolymphoidocytes;/,  large  monocytes.     (Simon.) 


SYMPTOMS  OF  INFLAMMATION  141 

ment)  and  invade  the  masses  of  bacteria,  or  surround  the  irritant  if 
non-bacterial  and  attempt  to  destroy  them.  These  cells  themselves 
are  killed  in  great  numbers  by  the  actions  of  the  product  of  the  bacteria, 
namely,  the  toxins. 

The  endothelial  leukocytes  appear  later  in  the  inflammatory  proc- 
ess, when  the  polynuclear  forms  are  diminishing  in  number,  acting 
as  a  sort  of  reserve  guard.  They  accumulate  to  counteract  the  toxins 
of  the  bacteria  and  to  attend  to  foreign  bodies,  carbon  and  free  fat. 
These  cells  destroy  certain  forms  of  bacteria  by  enveloping  them  in 
the  cell  structure.     Phagocyiosis  is  the  term  used. 

The  lymphocytes  are  seen  most  abundantly  after  the  inflammation 
has  existed  for  some  time,  and  are  quite  characteristic  in  what  we 
know  as  chronic  inflammation. 

Symptoms  of  Inflammation.— While  these  changes  are  taking  place 
in  the  tissues,  certain  symptoms  of  the  inflammatory  process  have 
appeared,  of  which  the  patient  is  very  conscious.  These  symptoms 
are  four,  to  which  a  fifth  is  sometimes  added.  They  have  been  called 
the  cardinal  signs  of  inflammation  and  are  classic.  These  are :  Rubor; 
calor;  tumor;  dolor;  the  fifth,  functio  l^sa;  translated  these  are:  red- 
ness; heat;  swelling;  pain,  and  impaired  function.  _    _ 

1.  The  redness  is  due  to  the  increased  flow  of  blood.  Hyperemia  is 
the  term  that  is  sometimes  used  to  distinguish  the  early  stage  of 
inflammation.  As  the  flow  begins  to  decrease,  the  color  begms  to 
become  bluish  in  appearance. 

2.  The  local  heat  at  the  site  of  the  inflammation  never  exceeds  the 
temperature  of  the  internal  organs,  although  it  may  be  above  the 
normal  temperature  of  the  part.  No  heat  is  produced  in  the  affected 
area.  The  increased  temperature  is  due  to  the  increased  rapidity  of 
circulation  and  to  the  increased  volume  of  blood. 

3.  The  swelling  is  produced  by  the  exudation  from  the  blood- 
vessels. 

4.  The  -pain  is  due  to  pressure  on  the  nerves  by  the  exudates.  It 
is  often  possible  to  count  the  heart  beat  by  the  exacerbations  of 
pain.  The  pain  is  most  severe  in  dense  structures,  especially  when 
the  inflammation  is  confined  in  bony  walls,  as  in  the  pulp  of  a  tooth. 
This  pain  is  sometimes  referred  to  a  point  distant  from  the  seat  of 
trouble,  as  for  example,  earache  in  case  of  pulpitis. 

5.  The  disturbance  of  function  is  especially  seen  m  the  eftect  on 
secretions,  which  many  times  are  prevented  or  suppressed  Also 
movement  may  be  limited,  as  seen  in  stiffness  in  a  joint  that  is  inflamed. 

The  Inflammatory  Exudate.— Associated  with  or  foflowmg  closely 
after  the  transmigration  of  the  white  cells,  there  is  an  exudation  of 
lymph  from  the  lymph  vessels,  the  purpose  of  which  is  to  neutralize 
or  to  reduce  the  chemical  activity  of  toxins  given  oft*  by  bacteria  or 
other  products  present  in  the  tissues.  The  exudation  of  lymph  is 
seen,  as  an  illustration,  in  a  mosquito  bite.  We  have  here  a  chemical 
poisoii,  and  we  get  all  the  changes  incidental  to  inflammation,     ihat 


142  INFLAMMATION 

is,  the  change  in  the  circulation;  the  increase  in  rapidity,  then  the  slow- 
ing down  of  the  blood  stream,  the  transmigration  of  the  leukocytes, 
and  finally  the  throwing  out  of  lymph.  This  is  a  small  inflammation, 
but  it  has  all  the  phenomena  of  a  more  extensive  one. 

If  at  this  point,  the  most  important  purpose  of  the  inflammatory 
reaction  has  been  accomplished,  namely,  to  counteract  or  neutralize 
the  agent  causing  the  injury,  the  inflammation  subsides,  the  early 
products  of  the  inflammatory  process  are  absorbed  and  the  tissues 
soon  return  to  a  normal  condition. 

Unfortunately,  however,  especially  where  bacteria  are  concerned. 
Nature  is  not  always  successful,  and  other  phenomena  appear.  Further 
exudates  are  thrown  out;  the  exudation  becomes  more  complicated, 
and  other  substances  besides  the  lymph  are  thrown  out.  These 
exudates  vary  under  different  conditions. 

Types  of  Exudation.- — I.  Serous  exudation  is  watery  in  consistency, 
and  is  quite  similar  to  lymph;  in  fact,  it  resembles  it  very  closely,  and 
some  writers  simply  regard  the  serous  type  as  an  unusually  free 
exudation  of  lymph.  In  this  form  the  lymph  spaces  are  particularly 
involved  and  the  swelling  is  known  clinically  as  edema.  This  is  seen 
sometimes  in  a  sprain.  Pressure  with  the  thumb  or  finger  over  the 
swollen  area  will  usually  leave  an  indentation,  where  the  serum  has 
been  forced  out  of  the  tissues  by  the  pressure.  This  identation 
gradually  disappears  as  the  pressure  is  removed  and  as  the  serum 
flows  in  again. 

Another  example  of  this  serous  type  of  exudate  is  a  blister  from  an 
ordinary  burn,  or  from  irritation,  or  friction. 

II.  Fibrinous  exudation  consists  of  leukocytes  and  the  formation 
of  fibrin  and  occurs  most  characteristically  in  the  form  of  a  membrane. 
A  good  illustration  of  this  is  the  membrane  formed  in  diphtheria. 

These  membraneous  exudates  vary  in  their  characteristics.  Some 
are  firmly  adherent  to  the  underlying  tissues,  while  others  may  be 
readily  peeled  off,  leaving  sometimes  a  bleeding  and  sometimes  a 
smooth  surface. 

III.  Suiypurative  exudation  is  the  most  frequent  and  most  impor- 
tant form,  and  is  characterized  by  the  formation  of  yus.  This  is  the 
most  common  ending  of  acute  inflammation,  especially  when  bacteria 
are  acting  as  the  injurious  agent. 

In  the  discussion  of  inflammation  caused  by  bacteria,  it  was  shown 
that  leukocytes  were  clustered  together  and  the  lymph  had  been  thrown 
out.  What  is  the  next  phenomenon  to  appear?  It  is  briefly  that  the 
large  number  of  leukocytes  which  gather  in  the  tissue  form  an  impair- 
ment of  the  nutrition  of  the  tissue  in  which  they  are  located;  and  we 
are  so  made  up  economicafly,  so  far  as  our  tissues  are  concerned,  that 
the  nutriment  supplied  to  the  tissue  is  not  sufficient  to  nourish  the 
tissue  itself  and  also  these  leukocytes,  with  the  result  that  the  tissue 
cells  themselves  lose  their  vitality;  and  then,  also,  the  leukocytes  in 
giving  battle  to  the  bacteria  are  destroyed  in  large  numbers,  either 


PLATE   VI 


•.•:'y.v>!. 


^•iSim:, 


^mm 


a,  typical  leukoblast;  b,  old  form;  c,  monocytoid  form;  d,  neutrophilic  myelocytes; 
e,  neutrophilic  metamyelocytes;/,  polymorphonuclear  neutrophiles.     (Simon.) 


SYMPTOMS  OF  INFLAMMATION  143 

by  the  bacteria  or  their  toxins.  This  lack  of  nutrition,  this  dying  of 
the  tissue  cells  in  which  the  inflammation  is  located,  and  the  death  of 
the  leukocytes  themselves,  cause  a  dissolution  of  the  tissue,  and  as  a 
consequence  there  is  a  cavity  filled  with  dead  leukocytes,  dead  tissue 
cells,  lymph  and  dead  and  living  bacteria,  which  forms  a  creamy 
fluid  called  pus.     Clinically  this  is  known  as  an  abscess. 

The  formation  of  an  abscess  marks  the  end  of  the  inflammation, 
so  far  as  the  tissues  themselves  are  concerned;  that  is,  the  inflamma- 
tory process  has  been  limited  and  localized. 

The  leukocytes  which  transmigrate  into  the  tissues  entirely  surround 
the  seat  of  injury  and /on??  a  protectimj  wall  against  further  invasion. 

If  it  were  not  for  this  action  of  the  leukocytes  in  forming  this  wall 
between  the  general  circulation  and  the  injurious  agent  in  the  form  of 
bacteria,  each  time  we  received  an  injury  infectious  in  its  nature, 
that  is,  of  bacterial  origin,  we  would  either  have  a  general  blood 
poisoning  because  injurious  products  would  be  taken  up  by  the  circu- 
lation, or  the  inflammation  would  extend  indefinitely  out  into  the 
tissues  until  our  bodies  were  wholly  consumed  by  the  inflammation. 
Therefore  this  formation  of  an  abscess,  while  disagreeable,  painful 
and  uncomfortable,  in  itself  is  an  excellent  thing,  because  it  prevents 
the  disturbance  from  becoming  a  general  one  of  very  serious  conse- 
quences. 

Occasionally  the  leukocytes  are  unable  to  control  the  local  action, 
or  perhaps  the  infection  began  in  the  circulation,  and  in  that  case 
general  blood  poisoning  or  septicemia  results.  This  is  a  very  serious 
condition.  But,  fortunately,  the  leukocytes  generally  form  an  actual 
resisting  force,  or  limiting  membrane,  through  which  the  bacteria  are 
unable  to  pass  and  inside  of  which  is  this  pus  cavity. 

The  next  question  that  naturally  arises  is,  what  becomes  of  the  pus 
and  this  wall  of  leukocytes?  The  tendency  of  all  abscesses  is  to 
evacuate  themselves;  that  is,  to  throw  off  their  contents,  and  get  rid  of 
the  secretion  that  exists.  The  method  of  doing  this  is  as  follows: 
The  fluid  elements  of  the  abscess  cavity,  or  the  pus,  increases  in 
amount,  and  the  increase  in  quantity  increases  the  pressure  around 
the  tissues,  and  as  this  fluid  element  continues  to  increase,  the  pressure 
becomes  greater  and  greater,  and  as  the  pressure  becomes  greater 
the  tissue  before  it  gradually  yields,  and  the  pus  finds  its  way  in  what 
has  been  classically  called  the  path  of  least  resistance.  This  act  of 
Nature  in  endeavoring  to  throw  off  the  pus  has  been  called  the  bur- 
rowing of  pus.  It  tries  hard  to  get  through  to  the  surface  of  the 
body,  or  to  a  cavity,  and  burrows  its  way  through  the  tissues  in  the 
path  of  least  resistance.  When  the  pus  has  finally  approximated  the 
surface,  we  have  what  is  known  as  pointing.  This  term  is  well  known. 
Years  ago  it  was  customary  to  poultice  any  inflammatory  condition 
to  bring,  as  they  said,  the  trouble  to  the  surface,  and  this  poulticing 
was  intended  to  hasten  the  action  of  the  pus  burrowing,  to  hasten 
the  pointing  of  the  abscess  so  that  the  contents  could  be  evacuated. 


144  INFLAMMATION 

If  an  abscess  is  not  surgically  opened  and  the  pus  discharged,  the 
tissues  will  spontaneously  rupture  and  the  pus  will  escape,  either  on 
the  surface  of  the  body  somewhere,  or  else  into  one  of  the  cavities  of 
the  body,  as  has  been  suggested.  For  instance,  if  an  abscess  on  the 
lower  jaw  results  from  an  inflamed  tooth,  the  path  of  least  resistance 
may  be  downward  and  a  large  swelling  occurs  under  the  jaw.  As 
the  pus  comes  closer  and  closer  to  the  surface  it  either  is  opened  and 
evacuated  surgically,  or  else  it  may  point  and  discharge  underneath 
the  chin.  If  there  is  an  abscess,  for  instance,  in  the  appendix,  and  it 
is  allowed  to  go  uncared  for  until  it  ruptures,  it  ruptures  into  the 
abdominal  cavity  and  peritonitis  results.  The  pus,  in  other  words, 
tries  to  escape  from  the  tissue  and  come  out  freely,  and  thus  relieve 
the  pressure  on  the  tissues  in  which  the  abscess  has  formed. 

The  channel  through  which  the  pus  passes  is  called  a  sinus,  and  the 
opening  on  the  surface  is  called  a  fistula.  These  two  terms  are  very 
common,  especially  in  inflammatory  conditions  connected  with  the 
mouth  and  teeth.  We  speak  of  a  sinus,  for  instance,  when  a  chronic 
abscess  discharges  into  the  mouth  over  a  tooth  on  the  gum.  The 
canal  or  channel  through  which  the  pus  escapes  to  the  surface  is  the 
sinus,  and  the  opening  on  the  gum  out  of  which  the  pus  comes  is 
the  fistula. 

If  the  abscess  is  a  very  superficial  one,  it  is  merely  a  simple  abscess 
of  the  skin.  When  the  pus  comes  through  the  surface  the  layers  of 
the  skin  may  be  destroyed,  leaving  more  or  less  of  an  open  wound 
of  a  very  superficial  nature.     This  condition  is  known  as  an  ulcer. 

Chronic  tiflammation. — Before  discussing  repair  or  what  takes  place 
after  the  pus  is  evacuated,  chronic  inflammation  may  be  briefly 
described.  Chronic  inflammation  is  the  result  of  a  continued  irrita- 
tion. It  may  follow  acute  inflammation,  or  it  may  start  as  inflamma- 
tion of  a  chronic  form.  Chronic  inflammation  is  a  very  different 
process  from  the  acute  form,  and  some  writers  have  gone  so  far  as 
to  say  that  chronic  inflammation  is  not  a  true  inflammation  at  all. 
The  essential  feature  of  chronic  inflammation  is  the  formation  of  new 
connective  tissue,  a  proliferation  of  the  fibroblast,  or  connective-tissue 
cell.  The  term  fibrosis  has  sometimes  been  applied  to  this  form  of 
tissue  change,  because  it  describes  the  condition  better  than  the  term 
chronic  inflammation. 

In  this  chronic  inflammatory  process,  hyperemia,  or  change  in  the 
bloodvessels,  that  is,  the  bringing  of  additional  blood  to  the  part, 
edema,  the  throwing  out  of  the  lymph  and  suppuration,  the  formation 
of  pus,  are  absent.  Instead  there  is  this  proliferation,  as  it  is  called, 
of  the  connective-tissue  cell,  and  the  throwing  out  of  some  of  the  white 
cells  of  the  blood,  particularly  the  lymphocytes.  The  chief  character- 
istics, then,  are  the  formation  of  connective  tissue,  the  fibroblastic 
proliferation  and  the  lymphocytic  infiltration  or  throwing  out  of  these 
lymphocytes.  No  pus  is  found  nor  other  symptoms  of  the  inflam- 
matory changes. 


SYMPTOMS  OF  INFLAMMATION  145 

Repair.— Repair  is  the  general  term  used  to  describe  the  processes 
taking  place  after  injury  and  exudation  caused  by  harmful  agents. 
The  repair  of  tissue  or  the  repair  of  the  injury  is  a  very  complicated 
subject  but  it  includes  three  divisions  which  will  be  briefly  described: 

First,  repair  includes  removal  of  foreign  bodies  of  all  sorts;  and  by 
foreign  bodies  is  meant  dead  cells  of  all  kinds:  (I)  Tissue  cells  that 
have  died  as  the  result  of  the  process,  (2)  leukocytes  of  the  polynuclear 
form,  (3)  endothelial  leukocytes,  (4)  bacteria  dead  and  alive. 

The  absorption  and  removal  of  foreign  bodies  such  as  sutures  should 
also  be  included.  There  may  be  an  operation  and  stitches  are  taken 
deep  in  the  body.  These  stitches  are  allowed  to  stay  there,  and  they 
are  removed  as  foreign  bodies,  and  this  is  part  of  the  function  of  repair. 
In  addition,  secretions  from  bacteriological  products,  the  toxins,  and 
in  some  cases  the  lime  salts  which  are  formed  as  the  result  of  the 
various  conditions  are  included;  in  fact,  the  removal  of  anything  that 
is  foreign,  or  is  not  of  service  in  the  tissue  is  one  of  the  functions  of 
repair. 

Second,  the  organization  of  fibrin. 

Third,  the  regeneration  of  cells  to  restore  the  part  which  has  been 
destroyed. 

I.  How  does  the  removal  of  the  foreign  bodies  take  place?  In 
a  word,  the  leukocytes,  or  white  cells,  change  somewhat  their  function, 
and  they  become  active  in  carrying  off  the  foreign  bodies. 

These  dead  tissue  cells  are  destroyed  and  removed  in  part,  a  little 
at  a  time.  The  bacteria  may  be  actually  digested  by  the  leukocytes 
after  being  taken  up  by  these  cells.  Very  frequently  under  the 
microscope  these  endothelial  cells  may  be  seen  with  several  bacteria 
in  their  protoplasm.  The  endothelial  leukocyte  is  especially  active 
in  this  part  of  the  process.     The  phenomenon  is  called  phagocytosis. 

II.  The  fibrinous  exudate  is  taken  care  of  by  the  connective- 
tissue  cells,  the  fibroblasts,  which  form  and  grow  into  the  fibrin  and 
gradually  replace  it. 

III.  The  regeneration  of  cells  is  the  growth  of  new  cells,  and  is 
brought  about  by  what  we  know  as  cellular  division,  or  mitosis. 
Under  stimulation,  the  cells  in  the  vicinity  of  the  wound  will  gradu- 
ally begin  to  multiply  and  fill  in  the  vacancy  that  is  caused  by  the 
destruction  of  the  tissue,  and  gradually  this  cavity  or  the  injury  due 
to  loss  of  tissue  is  replaced  by  new  cells,  which  have  divided  and 
redivided  and  divided  again. 

Clinically  speaking,  repair  or  the  healing  of  wounds  takes  place  in 
two  ways:  {1}  By  primary  heahng,  as  we  know  it,  called  healing  by 
first  intention;  and  (2)  by  secondary  healing,  or  healing  by  second 
intention,  or  healing  by  granulation  tissue. 

Healing  by  First  Intention. — To  illustrate  the  healing  by  first  inten- 
tion, let  us  assume  we  have  an  incised  wound.  After  the  bleeding 
is  stopped  the  wound,  which  is  the  result  of  a  cut  remains  filled  with 
blood,  and  this  blood  coagulates  and  forms  a  sort  of  plug  in  the 
wound.    This  plug  or  coagulated  blood  retracts  and  tends  to  hold 


146  INFLAMMATION 

the  edges  of  the  wound  together,  and  over  the  surface  a  crust  is 
formed,  which  is  nothing  more  than  dried  secretion,  dried  lymph 
plus  a  few  cells,  and  this  is  commonly  spoken  of  as  scab.  The  healing 
process  begins  at  once.  Of  course,  the  various  stages  of  inflammation, 
the  changes  in  circulation,  and  throwing  out  of  the  leukocytes  must 
occur,  but  all  of  the  cardinal  symptoms  of  a  true  inflammation  may 
not  be  present.  In  addition  to  the  throwing  out  of  the  leukocytes, 
the  connective-tissue  cells  become  active;  and  this  blood-clot,  which 
has  been  mentioned  above,  acts  as  a  sort  of  scaffolding,  upon  which 
the  connective  tissue  builds,  sending  out  little  prolongations  of  tissue. 
This  connective  tissue  gradually  replaces  the  blood-clot  and  the  edges 
of  the  wound  are  held  firmly  together.  Then  if  the  wound  is  on  the 
surface,  the  epithelial  coverings  will  send  out  prolongations  and  heal 
it  over  with  no  evidence  of  scar.  If  the  edges  of  the  wound  after  a 
cut  are  held  firmly  together,  for  instance,  with  plaster  or  a  bandage, 
very  little  connective  tissue  is  formed.  It  takes  very  little  new 
tissue  to  repair  the  wound;  but  if  it  is  a  gaping  wound,  more  material 
is  needed  to  repair  it;  and  where  a  portion  of  the  surface  of  the  skin 
is  lost  and  it  becomes  impossible  for  the  epithelial  cells  to  span  the 
breach,  the  connective  tissue  fills  it  in,  and  the  result  is  known  as  a 
cicatrix.  The  tissue  which  forms  is  called  cicatricial  tissue,  or  scar 
tissue.  This  has  a  very  great  tendency  to  contract.  As  these  new 
cells  become  older  they  contract  somewhat,  and  the  contraction  of 
scar  tissue  is  well  known.  The  scar  tissue  that  results  where  the 
epithelium  is  not  completely  restored,  for  instance,  on  the  hand,  is 
not  original  skin  tissue,  but  it  is  made  up  of  connective  tissue. 

Healing  by  Second  Intention. — It  has  been  shown  that  healing  by  first 
intention  has  nothing  to  do  with  infection;  that  is,  bacteria  have 
been  absent  in  the  changes  that  have  taken  place.  In  repair,  by 
second  intention,  however,  the  suppurative  process,  and  all  the  phe- 
nomena of  inflammation  with  the  formation  of  pus  and  the  evacuation 
or  throwing  out  of  pus  cells,  and  the  products  of  exudation  must  occur 
before  the  actual  healing.  When  this  takes  place,  the  cavity  which 
results  from  the  pus  is  filled  in  gradually  by  granulation  tissue  and 
connective  tissue  in  much  the  same  way  as  in  healing  by  first  inten- 
tion; but  there  is  much  more  tissue  to  be  restored,  and  the  healing 
process  may  be  slow,  particularly  if  the  cavity  is  large.  It  is  often 
possible,  after  the  pus  has  spent  itself  and  the  acute  symptoms  have 
subsided,  to  bring  the  edges  of  a  wound  together  and  have  it  heal  by 
first  intention,  but  that  is  not  customary.  If  instead,  in  this  type 
of  wound  the  opening  is  packed  with  gauze,  and  allowed  to  fill  in,  as 
we  say,  from  the  bottom,  the  granulation  tissue  fills  up  gradually,  and 
each  day  less  gauze  is  used  in  the  packing  until  the  cavity  is  filled  in 
solidly  with  this  connective  tissue.  This  healing  by  granulation  becomes 
very  important  under  some  conditions,  because  the  contraction  is 
sometimes  excessive.  If  there  is  a  severe  inflammation  or  a  bad 
abscess  of  the  cheek,  for  instance,  or  the  cheek  muscle  and  the  wound 
has  to  be  repaired  by  second  intention,  or  by  granulation  healing, 


PLATE   VII 


■.-W"      o 

/© 


• 


• 


Granulocytes.     (Simon.) 

a,  polynuclear  neutrophilic  leukocytes;  b,  polynuclear  eosinophilic  leukocytes;  c,  mast 
cells;  d,  eosinophilic  myelocytes;  e,  neutrophilic  myelocytes  (the  smaller  myelocytes 
represent  the  micro-,  the  larger  ones  the  macro-type) ;  /,  the  nucleus  here  has  just  under- 
gone division;  the  clear  space  is  a  vacuole. 


INFLAMMATION  OF  BONE  147 

after  a  while  this  contraction  of  the  cicatricial  tissue  may  be  so  great 
that  the  person  is  unable  to  extend  the  lower  jaw  or  open  the  mouth, 
and  thus  a  very  serious  condition  may  be  developed.  Fortunately 
this  is  not  common. 

Repair  then  in  general  is  the  effort  of  Nature  to  restore  the  tissues 
to  a  normal  condition  after  an  inflammation;  and  when  the  repair  is 
complete,  especially  if  it  is  by  first  intention,  the  parts  have  been 
restored  to  function  and  the  cells  resume  their  normal  relations. 

INFLAMMATION  AND  REPAIR  OF  BONE. 

Introduction. — We  ordinarily  regard  the  bones  as  more  or  less  station- 
ary in  the  structure  during  life,  but  they  are  in  fact  the  site  of  constant 
cellular  activity  and  are  subjett  to  continual  alterations  in  size,  shape, 
strength,  density  and  composition.  All  bones  possess  ridges  or 
processes  that  have  a  definite  anatomical  or  physiological  reason  for 
existence  but  which  begin  to  disappear  at  once  when  their  function  is 
fulfilled.  The  most  conspicuous  example  of  this  is  the  alveolar  proc- 
ess of  the  jaw  which  is  especially  designed  to  support  the  teeth. 
These  alveolar  processes  maintain  their  integrity  under  normal  con- 
ditions when  the  teeth  are  present,  but  are  absorbed  in  a  comparatively 
short  time  when  the  teeth  are  lost.  The  cells  that  serve  to  maintain 
the  integrity  of  bone  or  to  remove  unnecessary  portions,  as  the  case 
may  be,  are  the  osteoblasts  or  bone  formers,  and  the  osteoclasts  or 
bone  destroyers.    These  cells  are  also  active  in  repair  of  bone. 

INFLAMMATION  OF  BONE. 

Inflammation  may  occur  in  the  covering  membrane  or  periosteum 
of  bone  and  is  called  periostitis.  Ostitis  is  an  inflammation  of  the 
marrow,  and  osteomyelitis  is  the  term  used  when  all  parts  of  the  bone 
are  affected.  Clinically  it  is  quite  difficult,  especially  in  the  bones 
of  the  face,  to  differentiate  the  two  latter  forms  and  the  general  term 
osteomyelitis  is  commonly  used. 

Etiology. — Causes  of  inflammation  of  bones  are  similar  to  causes  of 
inflammation  of  other  tissues.  Traumatism  and  infection  are  the 
most  common  factors. 

Periostitis. — Inflammation  of  the  periosteum,  or  osteogenetic  mem- 
brane, may  be  acute  or  chronic.  In  the  acute  cases  the  periosteum 
becomes  swollen  and  exquisitely  tender  and  the  accompanying  pain  is 
usually  quite  severe.  This  condition  is  occasionally  seen  in  the  jaw 
after  the  injection  of  novocain  under  the  periosteum,  particularly 
when  care  has  not  been  taken.  If  infection  occurs,  a  subperiosteal 
abscess  may  result.  The  pericemental  abscess  so  frequently  seen 
along  the  root  of  a  tooth  or  its  socket  is  a  good  example  of  a  modified 
periostitis. 

Osteomyelitis. — The  term  used  to  describe  inflammation  of  the  bony 
structure  itself.  This  may  occur  from  a  previously  exciting  peri- 
ostitis or  may  be  the  direct  result  of  accident  or  infection.     This 


148  INFLAMMATION 

condition  is  quite  disposed  to  go  on  to  formation  of  pus  which  tends 
to  collect  in  cavities  of  the  bone  made  by  the  destruction  of  the  bone 
.cells. 

Necrosis  of  Bone. — The  end-result  of  many  cases  of  osteomyelitis. 
This  takes  place  when  the  nutrition  of  the  bone  has  been  interfered 
with.  The  bone,  as  a  result,  loses  its  vitality  and  death  or  necrosis 
sets  in. 

The  extent  of  the  necrosis  depends  on  the  severity  of  the  case. 
The  portion  of  the  bone  that  becomes  necrotic  is  called  the  seques- 
trum. In  the  larger  bones  this  sequestrum  may  occupy  a  central 
position,  that  is  in  the  marrow  cavity,  and  rarely  this  may  be 
observed  in  the  lower  jaw,  or  the  sequestrum  may  be  a  superficial 
or  subperiosteal  one. 

Repair  of  Bone. — The  repair  of  bone  is  similar  in  many  respects  to 
repair  of  soft  tissue,  but  differs  from  it  in  several  important  points. 
Any  dead  or  necrotic  bone  is  much  more  resistant  than  soft  tissue 
and  the  polymorphonuclear  and  endothelial  leukocytes  find  it  much 
harder  to  remove  and  absorb.  As  a  result  the  necrotic  bone  persists 
for  a  much  longer  time  in  the  lesion;  acts  as  a  real  foreign  body  and 
interferes  with  repair  so  long  as  it  is  not  removed  either  naturally  or 
surgically.  It  may  be  dissolved  very  gradually  by  the  action  of 
endothelial  leukocytes,  many  of  which  become  fused  to  form  the 
foreign  body  giant  cells  that  appear  so  characteristically  in  this  process. 
These  are  sometimes  called  osteoclasts  because  of  the  function  they 
perform. 

New  bone  is  not  found  in  a  solid  mass  but  in  narrow  trabeculse  with 
connective  tissue  richly  supplied  with  blood  between  them.  An  excess 
of  tissue  is  found  during  the  process  of  repair  which  occupies  more 
space  than  the  healed  bone  will  eventually  occupy.  Later  these 
trabeculse  fuse  more  or  less  completely  together  and  the  parts  not 
required  are  absorbed  by  the  osteoblasts.  In  repair  of  a  fracture  of 
bone,  osteoid  material  is  found  around  the  ends  of  the  fragments  at 
point  of  fracture  in  a  sort  of  tumor  mass  which  acts  as  a  kind  of  splint. 
This  formation  is  called  callus.  Later  the  excess  tissue  is  removed  so 
that  the  size  of  the  bone  at  point  of  fracture  is  nearly  the  same  as 
normal. 

There  is  considerable  difference  of  opinion  regarding  what  tissue 
furnishes  material  for  new  bone  growth.  It  is  very  well  accepted  that 
periosteum  and  endosteum  function  in  this  capacity  and  furnish 
fibroblasts  that  produce  osteoid  material  which  forms  the  basis  for 
new  bone.  It  was  formerly  thought  that  bone  cells  themselves  cannot 
do  this  and  many  still  hold  to  this  belief.  It  is  the  opinion  of  compe- 
tent observers,  however,  that  new  bone  growth  does  not  come  entirely 
from  the  periosteum  and  endosteum  but  does  come  from  the  bone 
cells  themselves. 

Note. — In  this  discussion  liberal  use  has  been  made  of  the  masterly 
exposition  of  the  subject  by  Prof.  E.  B.  Mallory,  to  whom  the  author 
is  deeply  indebted. 


CHAPTER  Vi. 

DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH. 

By  EDWARD  C.  KIRK,  D.D.S.,  Sc.D.,  LL.D. 

The  factors  involved  in  the  composition  and  mode  of  produc- 
tion of  deposits  and  accretions  upon  the  teeth  are  those  which  are 
intimately  connected  with  the  chemistry,  physiology  and  pathology 
of  the  saliva,  the  study  of  which  is  perhaps  one  of  the  most  important 
considerations  both  in  its  scientific  and  practical  aspects,  that  is 
engaging  the  attention  of  the  dental  profession,  for  it  is  through  the 
study  of  saliva  that  we  hope  to  ultimately  solve  some  of  the  most 
important  problems  with  which  we  have  to  deal  in  dental  practice. 

It  has  been  mainly  through  the  study  of  the  saliva  that  we  have 
arrived  at  some  very  definite  ideas  as  to  the  causation  of  dental  caries, 
and  through  the  study  of  saliva  we  have  also  learned  something  of 
various  other  diseases  to  which  the  teeth  and  soft  tissues  of  the  mouth 
are  subject,  and  it  is  through  the  study  of  the  saliva  we  learn  most 
about  the  deposits  or  accretions  that  are  commonly  spoken  of  as 
tartar  and  its  mode  of  formation.  After  all,  there  is  no  phase  of 
dental  study  that  is  of  more  immediate  importance  to  those  who  are 
pursuing  this  course  than  that  concerning  the  causes  which  lead  to 
the  formation  of  these  deposits  upon  the  teeth. 

As  for  the  word  "tartar,"  some  years  ago  in  one  of  the  popular 
magazines  there  appeared  an  article  by  a  physician  who  stated  that 
the  tartar  on  the  teeth  was  called  "tartar"  because  it  consisted  of 
tartrate  of  lime.  An  eminent  professor  of  chemistry  once  said  to  his 
class  dm-ing  a  lecture  that  he  never  had  understood  why  the  sulphate 
of  iron  was  popularly  called  copperas.  He  said  he  imagined  it  must 
have  been  called  copper  by  the  Dutch,  because  it  had  no  copper  in 
it.  By  the  same  mode  of  reasoning,  it  is  probable  that  this  medical 
man  called  these  deposits  tartar  because  there  is  no  tartaric  acid  in 
them. 

The  term  tartar  was  applied  by  the  alchemist  Basil  Valentine  to 
the  deposits  called  argols  in  wine  casks  consisting  essentially  of  potas- 
sium tartrate,  and  the  acid  derived  therefrom  was  called  tartaric  acid 
or  the  acid  of  tartaros.  Paracelsus  applied  the  term  much  more  widely 
to  include  earthy  deposits  from  animal  fluids  such  as  calculus  from  the 
saliva.  Tartar  consists  essentially  of  calcium  phosphate  or  phosphate 
of  lime  and  some  carbonate  of  lime  and  corresponding  magnesia  salts 
held  together  by  a  binding  material  that  we  call  mucin,  a  substance 
derived  from  the  mucus  of  the  saliva;  that  and  some  organic  matter 


150  DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 

such  as  food  particles,  and  the  bodies  of  dead  bacteria,  make  up  the 
bulk  of  what  we  call  "tartar." 

In  order  to  understand  the  formation  and  deposition  of  tartar  we 
must  first  know  something  about  the  saliva.  By  saliva  we  mean  that 
mucoid  fluid  which  we  find  in  our  mouths  most  of  the  time.  It  is 
is  not  always  flowing,  but  our  mouths  and  our  food  are  lubricated 
and  moistened  by  it.  This  saliva  is  manufactured  by  three  pairs  of 
glandular  structures  situated  in  the  region  of  the  mouth  which  pour 
their  secretions  into  the  oral  cavity.  The  secretions  of  these  several 
pairs  of  glands,  which  we  speak  of  as  the  salivary  glands,  differ  in 
their  composition.  Neither  do  all  of  these  glands  pour  their  secretion 
into  the  mouth  at  the  same  time,  but  under  different  circumstances 
and  in  response  to  different  kinds  of  stimuli,  namely,  the  stimulus  of 
food  or  the  stimulus  of  the  thought  of  food  or  the  stimulus  of  pain. 

You  are  all  familiar  with  the  common  expression  that  if  we  think  of 
this  or  that  kind  of  food  it  makes  our  "mouths  water."  This  is 
literally  true.  Under  the  psychic  stimulus  of  the  thought  of  food, 
especially  of  food  which  is  sapid  or  tasty,  the  salivary  glands  are 
encouraged  to  pour  their  secretions  into  the  mouth,  but  it  is  interesting 
to  note  that  different  kinds  of  foods  excite  the  secretion  of  different 
glands.  For  example,  the  physiological  chemist  Pavlow,  of  Petro- 
grad,  found  that  when  a  piece  of  fresh  meat  was  offered  to  a  dog  the 
flow  of  saliva  from  the  sublingual  and  submaxillary  glands  was  stimu- 
lated, but  not  that  from  the  parotid,  which  is  a  large  gland  situated  in 
front  of  the  ear. 

When  dry  food,  like  powdered  meat,  was  offered  to  the  dog,  the 
parotid  salivary  secretion  was  stimulated.  So  under  different  stimuli 
we  find  a  response  from  different  glands,  and  the  response  seems  to 
stand  in  very  close  relationship  to  the  character  of  the  food  that  exerts 
the  stimulus.  This  is  an  important  relationship  too,  because  dry 
foods,  for  example,  need  a  great  deal  of  moisture  for  two  reasons: 

(1)  For  converting  the  food  into  a  bolus  so  that  it  may  be  swallowed; 

(2)  for  furnishing  sufficient  water  to  the  food  in  order  to  dissolve 
its  soluble  elements  and  to  develop  its  taste.  Tasty  things  stimulate 
the  flow  of  saliva,  and  the  watery  secretion  of  the  parotid  gland  is 
necessary  in  order  to  dissolve  what  is  soluble  in  the  food  in  order 
to  bring  out  its  taste.  We  cannot  taste  anything  unless  it  is  soluble, 
no  more  can  we  smell  something  unless  it  gives  off  a  vapor  of  some 
sort.  So  that  gratification  of  the  sense  of  taste  is  secured  by  the 
solvent  action  of  the  parotid  saliva,  mainly,  upon  the  foods  that  we 
take  into  the  mouth  and  gratification  of  the  sense  of  taste  plays  an 
important  role  in  the  cycle  of  activities  that  are  related  to  normal 
bodily  nutrition. 

Besides  the  secretion  of  the  salivary  glands,  the  secretion  of  innumer- 
able mucous  glands  that  are  imbedded  throughout  the  whole  oral  or 
buccal  mucous  membrane,  the  lining  membrane  of  the  mouth,  is  added 
to  the  mixed  saliva,  and  it  is  the  secretion  of  these  mucous  glands 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  151 

that  gives  to  the  saliva  its  slimy  or  slippery  quality,  owing  to  the  sub- 
stance mucin  contained  therein. 

Mucin  is  a  very  important  constituent  of  the  saliva,  among  other 
things  it  has  a  very  direct  bearing  upon  tartar  formation,  but  its 
main  function  seems  to  be  that  of  a  lubricant.  Perhaps  you  all  know 
of  the  peculiar  technic  of  reptiles  when  they  feed.  A  boa  constrictor 
for  instance,  kills  its  prey,  which  may  be  a  half -grown  pig,  and  covers 
it  with  a  slimy  coating  so  as  to  lubricate  this  relatively  enormous 
mouthful,  and  to  render  its  passage  into  his  interior  as  easy  as  possible. 
In  a  minor  degree,  the  same  function  is  performed  by  the  lubricating 
exudate  of  the  mucous  glands  of  the  mouth  upon  the  bolus  of  food  in 
the  mouth  of  the  human  being. 

Beside  this  important  substance,  mucin,  the  saliva  contains  also  a 
peculiar  ferment  known  as  ptyalin,  the  function  of  which  is  to  begin  the 
digestion  of  starchy  substances  in  the  mouth.  Starch  as  such  is  not 
utilizable  as  food  by  the  body,  therefore  the  ptyalin  acts  upon  it,  con- 
verting it  by  degrees  into  a  kind  of  sugar,  maltose.  This  predigestion 
of  starch,  or  preparation  for  intestinal  digestion,  takes  place  in  the 
mouth,  hence  the  very  great  importance  of  thorough  mastication  of 
starches,  which  is  doubtless  the  main  justification  for  the  fad  of 
super-chewing  that  has  spread  over  the  country  under  the  name  of 
Fletcher  ism. 

Another  constituent  of  the  saliva,  though  perhaps  it  is  not  of  very 
great  importance,  has  been  exciting  a  great  deal  of  comment  in  the 
past  four  or  five  years;  that  substance  is  known  as  potassium  sul- 
phocyanate,  ordinarily  spoken  of  as  sulphocyanate.  It  may  be 
questioned  that  it  is  a  potassium  sulphocyanate,  but  some  kind  of 
sulphocyante  is  present  which  is  possibly  a  sodium  or  ammonium 
sulphocyanate.  It  has  the  peculiar  property  that  when  to  a  small 
quantity  of  saliva  a  drop  or  two  of  a  test  solution  of  perchloride  of 
iron  is  added,  if  the  sulphocyanate  is  present  it  causes  a  red  or  reddish 
coloration  of  the  saliva.  This  reaction  is  rather  dramatic,  and  has 
caused  a  great  deal  of  discussion  and  debate  as  to  its  significance 
which  thus  far  appears  to  be  unimportant. 

Sulphocyanate  was  at  one  time  supposed  to  have  a  very  important 
bearing  upon  caries  causation,  or  of  the  prevention  of  carious  action 
in  the  mouth,  but  recently  it  has  been  pretty  definitely  shown  that 
sulphocyanate  is  an  incidental  constituent  of  the  saliva,  and  that  it 
has  no  significance  except  as  a  waste  product  of  nutrition  related  to 
some  other  chemical  activities  in  the  body. 

In  addition  to  the  constituents  mentioned,  saliva  collected  in  a 
receptacle  will  show  certain  sediments,  solid  matter,  if  it  stands  for 
a  short  time.  Just  as  the  scarf-skin,  or  outer  layer  of  the  cuticle, 
separates  from  time  to  time,  so  does  the  mucous  membrane  of  the 
mouth  shed  its  epithelial  coating  into  the  saliva,  and  we  find  mixed 
with  the  saliva  these  epithelial  scales  from  the  buccal  mucous  mem- 
brane which  when  a  specimen  of  saliva  is  allowed  to  stand  for  a  time 
separate  as  sediment. 


152  DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 

We  find  also  as  corpuscular  elements,  the  leukocytes,  or  white 
blood  corpuscles,  which  gain  their  way  into  the  saliva.  They  have 
been  spoken  of  as  salivary  corpuscles,  but  they  are  really  white  blood 
cells  which  have  undergone  certain  changes  of  form. 

As  to  the  further  chemistry  of  the  saliva,  if  we  take  a  measured 
quantity,  and  evaporate  it  to  dryness,  we  find  a  small  residue  of  solid 
matter.  This  residue  consists  of  two  kinds  of  substances,  certain 
mineral  salts  which  we  speak  of  as  the  inorganic  constituents  of  the 
saliva,  and  another  kind  of  solid  matter  which  is  organic  in  character. 

The  total  solids  of  saliva  vary  considerably  in  amount.  It  is  difficult 
to  say  what  represents  the  total  quantity  of  solids  in  the  saliva,  but 
it  is  extremely  small  in  amount,  from  about  half  of  1  per  cent,  to 
possibly  1  per  cent,  of  the  total  saliva.  These  are  only  approximate 
figures,  because  the  composition  of  the  saliva  varies  constantly, 
depending  upon  the  time  of  day  when  the  sample  is  taken,  how  closely 
to  a  meal,  whether  after  vigoroys  prolonged  chewing,  after  drinking 
large  quantities  of  water,  or  after  abstaining  from  water  for  some  time. 
Saliva  becomes  more  concentrated  the  less  water  we  drink,  and  it 
becomes  more  dilute  in  accordance  with  the  quantity  of  water  drunk. 

The  normal  saliva  in  the  ideally  healthy  individual,  who  has  no 
caries  of  the  teeth,  no  deposits  upon  the  teeth  and  in  whom  the  various 
functions  are  properly  performed,  the  individual  who  is  living  up  to 
the  highest  state  of  physical  efficiency,  in  such  a  normal  human  being 
we  can  safely  say  the  saliva  is  colorless,  odorless  and  tasteless. 

If  the  saliva  develops  either  an  odor  or  a  characteristic  taste,  or  a 
color,  something  is  wrong;  it  is  not  a  normal,  but  a  pathological  saliva; 
something  has  gone  wrong  with  the  individual;  the  chemistry  of  his 
body  is  not  working  properly. 

When  studying  the  physical  appearance  of  a  quarter-  or  a  half- 
ounce  of  saliva  collected  in  a  test-tube,  we  find  that  in  addition  to  its 
limpidity,  its  clearness  or  opalescence,  a  slight  slimy  quality  due  to 
the  mucin  and  the  presence  of  sediment,  there  is  a  covering  of  froth 
upon  the  top  in  which  air  is  entangled.  Besides  which  the  saliva 
contains  dissolved  within .  itself  a  certain  quantity  of  carbon  dioxid. 
As  we  give  off  carbon  dioxid  from  the  lungs,  so  carbon  dioxid  is  present 
to  some  extent  in  the  saliva,  and  it  gradually  escapes  on  standing; 
hence  the  saliva  in  the  test-tube  soon  loses  its  froth,,  the  sediment 
settles  to  the  bottom,  and  we  have  a  column  of  this  clear,  odorless, 
tasteless  substance  above  a  layer  of  whitish  sediment. 

Any  variation  from  these  general  conditions  indicates  ill  health  of 
some  sort,  or  some  error  in  nutrition,  and  the  saliva  is  so  sensitive, 
chemically,  it  reflects  the  variations  in  composition  of  the  blood  stream 
so  accurately  that  we  can  utilize  it  for  the  study  of  the  nutritional 
condition  of  the  individual  at  the  time  when  the  specimen  is  taken. 

It  is  a  familiar  fact  that  physicians  have  for  years  been  studying 
the  urine  and  the  blood,  as  means  for  determining  the  condition  of 
bodily  nutrition,  but  investigation  has  brought  forth  the  fact  that  the 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  153 

saliva  is  almost  as  important  an  index  of  the  condition  of  nutrition  for 
the  time  being  as  either  of  these  other  fluids  mentioned. 

When  the  saliva  is  poured  from  the  glands  into  the  mouth  it  comes 
into  an  entirely  new  environment,  that  is  to  say,  as  it  issues  from  the 
gland  it  is,  comparatively  speaking,  sterile;  it  is  not  infected  with  bac- 
terial elements,  we  do  not  find  the  bacteria  in  the  saliva  as  it  issues 
from  the  glands,  but  it  issues  into  a  cavity  that  is  infected  on  all 
surfaces;  in  fact,  it  is  poured  into  that  portion  of  the  human  anatomy 
which  is  the  portal  of  entry,  for  nearly  all  of  the  bacterial  organisms 
that  enter  the  body,  and  the  saliva  is  necessarily  subjected  to  the 
influence  of  these  microorganisms. 

The  organisms  that  infect  the  mouth  are  not  only  myriad  in  number, 
but  they  are  of  an  infinite  variety  and  they  produce  different  effects 
upon  the  saliva.  Let  us  consider  a  little  more  closely  the  nature  of 
that  action  in  general.  It  is  a  familiar  fact  that  if  a  quantity  of  milk, 
for  example,  is  exposed  to  the  atmosphere  for  a  sufficient  length  of 
time,  especially  on  a  reasonably  warm  day,  the  milk  in  the  course 
of  time  undergoes  changes  and  becomes  sour,  as  we  say.  First,  it 
develops  a  sour  taste,  then  becomes  curdled,  and  if  it  is  left  to  stand 
still  longer  the  sourness  disappears  and  it  becomes  putrid,  developing 
a  very  disagreeable  odor,  as  it  undergoes  decomposition.  Modern 
bacteriology  has  settled  the  nature  of  these  processes.  They  are 
processes  of  decomposition  or  of  tearing  apart  of  the  various  complex 
compounds  that  we  find  in  milk  into  simpler  substances. 

Milk  contains  sugar,  nitrogenous  or  proteid  matter  in  the  form  of 
cheese,  or  casein,  it  contains  water  and  fats.  Each  one  of  these  sub- 
stances seems  to  have  a  selective  quality  for  certain  kinds  of  bacteria, 
some  of  which  attack  the  sugar,  for  example;  others  will  only  attack 
the  caseous  portion,  the  curd  of  the  milk;  other  germs  attack  the  fat. 
Butter,  for  example,  when  it  becomes  rancid,  forms  a  particular  kind 
of  acid,  butyric  acid,  as  it  is  called.  As  the  sugar  element  in  the  milk 
undergoes  decomposition,  it  becomes  sour  just  as  the  sugar  in  cider 
is  converted  into  vinegar,  or  alcohol,  as  the  case  may  be,  through  the 
agency  of  bacterial  action. 

Upon  the  same  principle  these  various  substances  in  the  saliva, 
mucin,  animal  matter  and  sometimes  sugar,  which  is  formed  by  the 
action  of  the  ptyalin  upon  starchy  matter  in  the  mouth  are  decomposed 
by  the  activity  of  certain  special  kinds  of  bacteria  and  produce  what 
are  designated  in  chemistry  as  typical  or  characteristic  kinds  of  end- 
products,  for  example,  acid  substances;  or  they  may  produce  ill- 
smelling  substances,  hydrogen  or  ammonium  sulphide  due  to  putre- 
faction or  substances  like  ptomains  or  toxins  which  have  a  specific 
poisonous  action  upon  the  tissues  with  which  they  come  in  contact. 

Incidentally  caries  or  decay  of  the  teetjh  is  produced  the  same  way. 
Thus  we  see  the  importance  of  the  study  of  the  saliva  in  relation  to 
the  manner  in  which  it  is  decomposed  through  the  agency  of  bacteria. 
From  all  this  we  may  also  deduce  the  immense  importance  of  a  clean 


154  DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 

mouth,  not  only  as  regards  the  integrity  of  the  teeth  and  the  tissues 
about  the  teeth  and  the  mouth  itself,  but  as  related  to  the  general 
health  of  the  individual.  The  question  of  a  clean  mouth  is  not  a  matter 
of  sentiment  alone,  or  a  matter  of  aesthetics,  but  it  is  fundamentally 
a  question  of  health. 

Since  decomposition  of  the  saliva  is  brought  about  through  the 
agency  of  a  large  variety  of  bacterial  forms  constantly  inhabiting  the 
mouth,  and  since  the  end-products  of  this  bacterial  action  are  so  varied, 
and  in  most  instances  either  poisonous,  or  capable  of  exerting  corrosive 
action  upon  the  tooth  structure,  it  is  evident  that  the  best  time  to  get 
rid  of  the  conditions  which  result  from  these  fermentative  and  putre- 
factive processes  that  take  place  in  the  mouth,  is  at  the  beginning,  and 
that  by  doing  so  we  can  successfully  prevent  not  only  diseases  of  the 
teeth,  but  many  diseases  which  affect  the  entire  body. 

In  connection  with  the  processes  of  decomposition  through  the 
agency  of  bacteria,  a  number  of  phenomena  manifest  themselves. 
In  the  first  place,  under  certain  conditions  there  is  the  production  of 
a  peculiar  kind  of  deposit  upon  the  teeth  which  has  been  spoken  of 
as  the  bacterial  plaque.  The  bacterial  plaque  is  very  important  in 
many  ways.  In  the  first  place,  it  represents  the  first  step  in  the  process 
of  that  disintegration  of  tooth  structure  which  we  call  dental  caries  or 
tooth  decay.  Broadly  speaking,  we  cannot  have  dental  caries  excepting 
through  the  agency  of  the  bacterial  plaque.  Viewed  simply  from  a 
physical  point  of  view,  a  bacterial  plaque  is  a  deposit  upon  a  tooth 
surface  which  localizes  the  process  of  decay.  The  function  which  the 
bacterial  plaque  performs  in  localizing  the  process  of  tooth  decay  at 
certain  points  is  the  factor  which  determines  the  principal  character- 
istic of  tooth  decay,  namely,  that  of  cavity  formation. 

Let  us  for  a  moment  examine  the  nature  of  this  deposit  called  the 
bacterial  plaque.  Recall  for  the  purpose  of  this  argument  the  fact 
that  the  saliva  contains  first  of  all  mucin  in  solution.  In  order  to  have 
a  solution  of  mucin  in  the  saliva  we  must  have  an  alkaline  reaction  of 
the  saliva,  because  mucin  is  not  soluble  in  an  acid  fluid.  If  we  take  a 
specimen  of  saliva  and  add  a  drop  of  any  kind  of  acid  to  it,  acetic 
acid,  lactic  acid,  sulphuric  acid,  citric  acid,  etc.,  we  shall  immediately 
see  what  we  call  a  precipitate  which  looks  as  if  something  in  the 
saliva  had  been  cooked,  as  in  the  cooking  of  the  white  of  an  egg. 
That  happens  instantly  when  mucin  comes  in  contact  with  any  acid. 

One  of  the  acids  which  is  most  prompt  to  cause  the  precipitation 
of  mucin  is  lactic  acid,  the  acid  that  is  produced  when  milk  sours. 
Lactic  acid  is  instantly  produced  in  the  mouth  by  the  action  of  cer- 
tain forms  of  bacteria  upon  sugars  found  in  or  taken  into  the  mouth. 

Sugars,  as  we  know,  are  produced  in  the  mouth  by  the  action  of  the 
ptyalin  of  the  saliva  which  converts  the  starch  into  sugar.  As  long 
as  sugar  is  thus  formed  certain  classes  of  bacteria  act  upon  it  and  split 
it  up  into  lactic  acid.  These  lactic-acid-producing  organisms  being 
constantly  present,  fermentation  goes  on  and  lactic  acid  is  produced 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  155 

as  long  as  there  is  something  for  the  organisms  to  Uve  upon.  Just  the 
moment  that  a  point  (considering  a  bacterium  as  a  point)  of  acid 
production  is  set  up  in  the  saHva  there  occurs  a  precipitation  around 
that  point  of  insoluble  mucin,  and  when  the  action  is  started  by  the 
lodgement  of  lactic-acid-producing  organisms  upon  a  tooth  surface 
where  they  may  develop  and  multiply  undisturbed  in  protected  loca- 
tions the  process  continues  until  what  we  call  a  bacterial  plaque  is 
formed.  These  plaques  are  localized  upon  all  tooth  surfaces  that  are 
protected  from  the  friction  of  food  or  of  the  tongue  or  lips,  and  in 
places  that  are  not  kept  thoroughly  polished  and  clean,  especially  in 
the  class  of  mouths  that  are  susceptible  to  dental  caries. 

It  will  be  readily  understood  that  the  acid  which  is  manufactured 
at  the  point  localized  by  the  bacterial  plaque  is  constantly  disinte- 
grating the  tooth  structure  upon  which  it  has  formed  and  breaking  it 
down.  Thus  we  have  a  deposit  produced  from  the  saliva  and  from 
conditions  existing  in  the  saliva  which  is  the  first  step  in  the  process 
that  we  speak  of  as  dental  caries. 

The  plaques  are  not  ordinarily  visible  to  the  naked  eye,  but  there 
has  been  introduced^  what  is  denominated  a  "disclosing  solution" 
containing  iodin,  which  renders  them  visible.  By  applying  tincture 
of  iodin  to  mucin  we  secure  a  color  reaction,  that  is  to  say,  it  pro- 
duces a  brownish  or  reddish-brown  tint  deeper  than  that  of  the  iodin, 
especially  if  certain  of  the  sugars,  maltose,  for  example,  be  present. 
If  we  paint  the  tooth  with  iodin  or  spray  it  with  a  solution  of  iodin, 
in  the  course  of  time  we  will  find  that  the  iodin  has  stained  certain 
portions  of  the  tooth  to  a  darker  tint  than  others,  owing  to  the  fact 
that  the  plaques  have  taken  up  the  iodin,  combined  with  it  and  formed 
a  dark  brownish  stain.  The  formula  of  Skinner's  disclosing  solution 
is  as  follows: 

Iodin  crystals 50  grs. 

Potassium  iodid 15  grs. 

Zinc  iodid 15  grs. 

Glycerin       ... 4  dr. 

Water ' 4  dr. — M. 

As  an  adjuvant  to  the  disclosing  solution,  however,  another  step  or 
stage  has  been  suggested  by  H.  C.  Ferris,  and  that  is,  the  spraying  of 
the  surface,  after  it  has  been  treated  with  the  iodin  solution,  with  a 
boiled  starch  solution.  It  should  be  remembered,  however,  that  starch 
and  iodin,  no  matter  how  they  are  put  together,  produce  a  very  dense 
blue  color,  and  unless  one  is  careful  in  making  this  test,  the  starch  may 
apparently  disclose  plaques  where  they  do  not  exist.  Hence  the 
tooth  should  be  rinsed  thoroughly  before  the  application  of  the  second 
member  of  the  disclosing  solution  is  made  in  order  to  remove  excess  of 
iodin.     As  a  matter  of  fact,  a  plaque  is  disclosed  with  sufficient  clear- 

'  F.  H.  Skinner,  Dental  Cosmos/  1912,  p.  43. 


156  DEPOSITS  AND  A  CCRETIONS  UPON  THE  TEETH 

ness  by  the  use  of  the  ordinary  official  tincture  of  iodin,  7  per  cent., 
without  subsequent  appHcation  of  starch  solution. 

There  may  be  other  sources  of  plaque  formation,  but  the  explana- 
tion given  indicates  the  general  principle  which  accounts  for  these 
soft,  slimy,  fairly  adhesive  deposits  upon  the  teeth,  which  can  be 
readily  rubbed  off  by  the  application  of  fine  pumice  on  an  orange- 
wood  stick,  if  the  rubbing  and  polishing  is  thoroughly  and  carefully 
done.  It  does  not  require  the  instrumentation  that  we  speak  of  as 
"scaling'^  to  remove  deposits  of  this  class. 

In  the  precipitation  of  mucin  by  lactic  acid  we  have  the  general 
principle  involved  in  practically  all  of  the  deposits  of  that  character. 
These  may  be  localized  or  there  may  be  a  general  precipitation  of 
mucin  upon  the  teeth,  carrying  with  it  particles  of  food  or  debris  of 
various  sorts,  which,  if  not  removed,  condenses,  grows  harder,  more 
tenacious  and  more  difficult  to  remove,  though  when  first  deposited 
it  is  very  soft  in  character. 

We  come  now  to  a  consideration  of  an  entirely  different  class  of 
deposits  which  are  of  the  true  tartar  type,  namely,  the  mineral  deposits 
upon  the  teeth.  The  formation  of  tartar  is  a  most  complicated  process 
and  constitutes  one  of  the  puzzles  of  the  chemistry  of  the  mouth.  What 
we  do  know  about  it  is  this :  Chemical  analysis  of  these  hard  deposits 
called  tartar  shows  them  to  consist  mainly  of  calcium  phosphate, 
some  calcium  carbonate,  the  bodies  of  dead  bacteria,  debris  of  food, 
food  particles,  all  bound  together  by  mucin. 

An  English  investigator,  Mr.  Rainey,  about  fifty  years  ago,  under- 
took a  study  of  the  mode  of  formation  of  shells  of  various  sorts,  and 
he  was  led  into  some  experimentation  with  reference  to  the  changes 
that  take  place  in  certain  kinds  of  earthy  precipitates  like  carbonate 
of  lime  under  varying  conditions,  as  for  example,  when  these  earthy 
substances  were  precipitated  in  a  solution  which  contained  a  material 
like  gelatin,  gum  arable  or  egg  albumen,  or  what  is  termed  in  chem- 
istry, colloidal  substances.  He  found  that  the  carbonate  of  lime 
was  precipitated  from  a  watery  solution  in  a  more  or  less  crystalline 
character,  but  if  the  smallest  quantity  of  glue,  albumin,  gelatin  or 
other  glue-like  substance,  was  added  to  the  water  in  which  the  pre- 
cipitation took  place  the  deposit  instead  of  being  of  a  crystalline 
character  was  made  up  of  little  spherical  bodies  that  were  more  or 
less  translucent.  The  precipitate  formed  very  slowly  and  this  investi- 
gator found  that  these  minute  globular  masses  side  by  side  tended  to 
increase  in  size  by  additions  to  their  exterior,  this  increase  in  size 
continuing  until  two  of  these  bodies  would  come  together  and  coa- 
lesce; then  another  one  would  grow  up  to  this  mass  and  they  would 
coalesce,  so  that  gradually  it  assumed  the  appearance  of  a  mass  of 
marbles  glued  together  or,  of  a  mulberry  mass. 

This  investigation  led  others  to  continue  the  observations  and 
finally  it  was  shown  that  the  process  of  precipitation  and  molecular 
coalescence  is  at  the  bottom  of  a  number  of  very  important  processes 


DEPOSITS' AND  ACCRETIONS  UPON  THE  TEETH  157 

not  only  in  the  human  body,  but  in  the  mode  of  growth  of  the  shells  of 
mollusks  and  the  pearl  formation  in  the  oyster,  for  example.  On 
further  investigation  it  was  found  that  the  pathological  conditions 
that  involve  stone-like  concretions  in  the  kidney  or  the  bladder,  con- 
cretions of  a  calcareous  character  that  are  found  sometimes  in  the 
ear  and  various  parts  of  the  body,  or  in  old  abscesses  that  have  under- 
gone repair,  all  arose  after  the  same  principle  of  coalescence  of  the 
precipitate  of  an  earthy  salt  in  combination  or  in  contact  with  a 
colloidal  or  glue-like  basis  which  acted  as  a  binding  material. 

Precipitations  of  the  earthy  salts,  phosphates  and  carbonates,  that 
were  held  in  solution  in  the  saliva,  when  they  take  place  in  the  human 
mouth,  combine  with  the  glue-like  substance  in  the  saliva  which  we 
have  spoken  of  as  mucin,  and  are  bound  together  by  the  mucin  to 
form  the  mass  called  tartar  which  deposits  itself  upon  the  teeth. 
Tartar  varies  in  a  great  many  ways;  it  varies  in  the  rapidity  with 
which  it  forms,  it  varies  in  the  position  in  which  it  is  deposited,  and 
above  all  it  varies  in  its  density,  the  tenacity  with  which  it  adheres 
to  the  tooth  surface  and  its  toughness. 


Fig.  92. — Specimens  of  parotid  tartar;  actual  size. 

Certain  classes  of  tartar  undergo  very  rapid  formation  and  enor- 
mous development.  Masses  of  tartar  weighing  as  much  as  from  two 
hundred  and  fifty  to  three  hundred  grains  are  reported.  It  seems 
incredible  that  any  human  being  could  tolerate  in  his  mouth  a  mass 
of  tartar  larger  than  a  pigeon's  egg  attached  to  the  buccal  surface  of 
the  molar  teeth,  yet  such  instances  are  by  no  means  infrequent.  Tar- 
tar which  is  formed  rapidly  and  in  large  masses  is  usually  relatively  soft 
and  friable  and  can  be  readily  removed  by  proper  instrumentation. 

Every  dentist  has  had  patients  with  the  idea  in  their  minds  that 
tartar  was  protective  to  the  teeth  and  for  that  reason  they  objected 
to  having  it  removed.  It  is  true  to  a  great  extent  that  teeth  upon 
which  that  kind  of  tartar  is  deposited  rarely  decay,  not  because  the 
tartar  is  protective,  but  because  conditions  that  cause  the  deposition 
of  the  tartar  are  precisely  the  opposite  of  those  that  favor  caries  of 


158 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 


the  teeth.  When  such  enormous  accumulations  are  removed  from  the 
teeth  the  patients  are  often  surprised  that  the  teeth  do  not  come  out 
with  the  removal  of  the  deposit. 


Fig.   93. — Sublingual  tartar  on  a 
lower  incisor. 


Fig.  94. — Sublingual  tartar  on  a 
lower  canine. 


This  kind  of  tartar  will  form  upon  artificial  dentures  just  as  readily 
as  upon  the  surfaces  of  the  natural  teeth,  and  it  is  usuallv  found  at 


Fig.  95. — Partial  denture  clasped  to  first  and  second  molars,  which  have  been  lost  by 
deposition  of  parotid  tartar. 

positions  opposite  the  orifices  of  the  ducts  of  the  salivary  glands. 
For  the  same  reason  we  find  these  enormous  masses  ordinarily  upon 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  159 

the  buccal  surfaces  of  the  molars  and  upon  the  lingual  surfaces  of 
the  lower  teeth  occupying  positions  almost  opposite  the  openings  of 
the  salivary  ducts  (see  Fig.  95). 

The  question  of  why  this  is  so  is  the  chemical  problem  that  we 
are  confronting.  This  is  what  we  know:  that  calcium  phosphate  as  it 
exists  in  tartar  is  not  the  same  kind  of  calcium  phosphate  that  exists 
in  solution  in  the  saliva;  that  is  to  say,  after  it  reaches  the  mouth 
it  undergoes  some  chemical  change,  the  nature  of  which  may  be  illus- 
trated as  follows:  One  of  the  popular  drinks  advertised  at  the  soda 
fountains  is  "Acid  Phosphate."  Calcium  phosphate  or  lime  phos- 
phate, chemically  speaking,  is  a  term  applied  to  a  group  of  compounds 
of  which  there  are  two  distinct  kinds.  One  contains  more  lime  in 
proportion  to  the  phosphoric  acid  than  does  the  other.  The  one  which 
contains  less  lime  in  proportion  to  the  phosphoric  acid  is  designated 
as  acid  phosphate,  which  is  soluble  in  water,  and  has  acid  properties; 
whereas  the  other  phosphate  which  is  designated  as  basic  phosphate 
contains  a  larger  proportion  of  lime  and  is  insoluble  in  water. 

If  we  add  to  the  acid  phosphate  a  little  more  lime,  we  convert  it 
into  basic  phosphate;  and  because  of  its  relative  insolubility  it  would 
fall  out  of  solution  as  a  sediment  or  precipitate.  A  similar  process 
occurs  in  the  deposition  of  this  phosphate  as  tartar  in  the  mouth. 
It  is  in  a  state  of  acid  combination  in  the  saliva.  Possibly  it  is  the 
content  of  carbonic  acid  in  the  saliva  which  holds  the  phosphate  in 
solution,  and  when  the  carbonic  acid  escapes  from  the  saliva,  the 
phosphate,  having  nothing  to  hold  it  in  solution,  falls  down  as  a 
precipitate. 

Mucin  acts  as  a  glue-like  binding  material  to  the  small  earthy 
particles  of  phosphate  and  fastens  them  together  and  when  the  pro- 
portion of  mucin  to  the  calcium  phosphate  is  in  certain  ratio  the  mass 
may  be  so  dense  and  adhesive  that  it  is  almost  impossible  to  cut  it 
with  a  steel  instrument  or  scrape  it  from  the  tooth  surface. 

The  escape  of  carbonic  acid  is  one  of  the  means  by  which  we  think 
the  earthy  materials  of  the  saliva  are  precipitated.  If  we  take  any 
alkaline  substance  into  the  mouth,  thereby  adding  free  alkali  to  the 
saliva,  we  are  likely  to  cause  a  precipitation  of  the  lime  salts. 

There  is  always  a  certain  amount  of  ammonia,  produced  by  the 
chemistry  of  nutrition,  that  issues  from  the  lungs  with  the  expired  air, 
and  if  there  is  enough  ammonia  produced  in  a  given  case  to  impart  a 
definite  free  alkalinity  to  the  saliva,  then  precipitation  of  the  lime 
salts  takes  place  or  ammonia  may  be  produced  in  the  mouth  by  putre- 
faction, decomposition  of  animal  substances  causing  tartar  formation 
in  unclean  mouths. 

There  is  another  suggested  mode  of  tartar  formation.  Dr.  H.  H. 
Burchard  found  that  when  fermentation  is  going  on  in  the  mouth 
with  production  of  lactic  acid  in  small  quantities  the  mucin  is  precipi- 
tated and  the  coagulated  mass  of  mucin  tends  to  gather  within  itself 
these  earthy  salts,  just  as  a  net  drawn  through  a  stream  would  gather 


160  DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 

up  fish;  this  mass  is  deposited  upon  the  teeth,  and  condenses  more 
and  more,  forming  tartar. 

Tartar  has  been  thus  produced  artificially  out  of  the  mouth,  by 
taking  saliva  rich  in  calcium  salts  and  adding  small  quantities  of 
dilute  lactic  acid,  causing  precipitation  when  a  hard  material  of  a 
dark  greenish  shade  is  produced,  physically  similar  to  the  deposits 
that  we  find  upon  the  teeth. 

One  of  the  most  interesting  examples  of  tartar  formation  is  that 
observed  upon  the  teeth  of  the  natives  of  Indo-China  and  the  Malay 
Archipelago.  They  are  habituated  to  the  chewing  of  the  betel  nut. 
This  use  of  the  betel  nut  as  a  masticatory  is  very  prevalent  throughout 
Indo-China  and  the  Malay  Archipelago. 

Habitual  chewing  of  the  betel  nut,  in  the  course  of  a  short  time, 
causes  the  teeth  to  become  stained  to  a  very  dark  reddish  brown  of 
about  the  color  of  the  exterior  of  a  chestnut,  and  enormous  deposits 
of  tartar  quickly  aggregate,  so  that  the  teeth  become  distorted  in 
appearance  and  position  and  are  very  quickly  lost  from  their  sockets. 
It  is  not  infrequent  that  young  people  not  over  twenty-five  years 
of  age  are  rendered  completely  toothless  by  the  habit  of  betel-nut- 
chewing. 

The  shavings  of  betel  nut  are  wrapped  up  in  pieces  of  the  leaf  of  a 
certain  kind  of  plant  called  Penang  pepper,  along  with  some  aromatic 
spices  such  as  catechu  or  cloves,  or  cardamom  seed,  according  to  the 
taste  of  the  betel-nut-chewer,  to  give  it  an  aromatic  flavor.  Then 
about  the  quantity  of  half  a  small  spoonful  of  lime,  made  by  burning 
oyster  shells,  is  sprinkled  all  over  this  mass  to  develop  the  flavor. 
This  morsel,  rolled  up  in  the  green  pepper  leaf,  is  very  carefully  tucked 
away  in  the  cheek.  It  causes  a  free  flow  of  saliva  tinged  with  a  red 
color.  The  addition  of  the  lime,  which  develops  the  flavor,  is  what 
causes  the  trouble.  The  acid  or  soluble  phosphate  of  lime  in  the  saliva 
upon  the  addition  of  this  extra  lime,  is  converted  into  the  insoluble 
form  of  phosphate  and  precipitated  on  the  teeth  (Figs.  96,  97  and  98). 

The  foregoing  is  an  example  of  the  formation  of  tartar  due  to  change 
in  the  chemical  composition  of  the  lime  salts  of  the  saliva  from  a 
soluble  form  into  an  insoluble  form. 

The  hardness  of  the  tartar  depends  upon  the  amount  of  its  lime 
constituent  as  related  to  the  mucin  constituent.  The  hardest  forma- 
tions of  tartar  contain  more  of  the  glue-like  or  mucinous  element  than 
do  the  more  friable  and  easily  broken-down  forms.  The  hardest 
tartar  formed  is  found  just  under  the  gum  margin.  The  large  masses 
that  are  attached  to  the  free  surfaces  of  the  teeth  opposite  the  ducts 
of  the  glands  are  usually  soft  and  easily  removed  regardless  of  size, 
but  the  rings  of  tartar  underneath  the  gum  margin,  the  hard  scales 
of  tartar,  are  the  most  difficult  of  removal.  It  is  this  kind  of  tartar 
that  contains  the  largest  proportion  of  organic  binding  material, 
because  the  deposit  of  tartar  at  that  point  sets  up  an  irritation  of  the 
gum  tissue  and  causes  the  weeping  out  from  the  gum  tissue  of  the 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  161 

albuminous,  serous  portion  of  the  blood  which  combines  with  this 
deposit  and  forms  a  very  hard,  tenacious  mass. 


Fig.  96. — Lower  incisor  almost  completely 
encrusted  with  betel  tartar. 


Fig.  97. — Lower  canine  covered  with 
betel  tartar. 


Fig.  98.— Lower  incisors  lost  from  deposit  of  betel  tartar.    As  they  gradually  loosened 
trom  the  encroachment  of  the  tartar  they  were  bound  together  with  fine  brass  wire  by  a 
native  dentist,  to  give  them  firmness  by  mutual  support 
11 


162  DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 

Farther  down  upon  the  roots  of  the  teeth  we  frequently  find  deposits 
of  another  form  of  tartar,  which  is  probably  not  salivary  in  origin. 
It  is  spoken  of  as  serumal  tartar  and  is  derived  from  the  serum  of  the 
blood.  From  a  chemical  standpoint  it  is  practically  a  formation  of 
the  same  character  but  it  originates  differently.  So  far  as  we  know, 
this  serumal  tartar  which  is  situated  deep  down  upon  the  roots  of  the 
teeth  and  not  connected  with  saliva  in  its  origin,  is  the  result  of  some 
primary  inflammatory  conditions  upon  the  tooth  root.  It  is  not  neces- 
sary to  go  into  the  causes  of  such  preceding  inflammatory  conditions 
which,  instead  of  breaking  out  as  abscesses,  have  healed  spontaneously 
by  what  we  call  the  process  of  resolution,  by  which  is  meant  that  the 
bacteria  which  set  up  the  inflammation  have  died.  They  have  been 
killed  by  the  resisting  forces  of  the  body  itself  and  the  inflammatory 
process  has  stopped,  and  the  tissues  have  undergone  repair,  but  the 
dead  bacteria  and  the  broken-down  tissue  constituting  pus  has  grad- 
ually become  dehydrated,  and  there  is  left  a  cheesy  mass  which  later 
on  has  become  saturated  with  lime  salts  derived  from  the  blood 
stream  itself.  These  lime  salts  combine  with  this  cheesy  mass  result- 
ing in  a  tartar-like  formation  in  which  the  cheesy  mass  of  colloidal 
organic  matter  takes  the  place  of  the  mucin  in  saliva  as  the  binding 
material. 

Tartar  formed  in  that  way  is  a  mechanical  irritant  to  the  surrounding 
tissues,  making  them  subject  to  subsequent  infections.  The  tartar 
acts  as  a  foreign  body  in  the  tissue  setting  up  irritation,  infection  fol- 
lows and  the  process  is  repeated  with  continued  growth  of  tartar,  or 
the  abscess  may  break  at  the  gum  margin  and  a  pyorrheal  pocket 
may  thus  be  formed.  The  pus  pockets  in  pyorrhea  may  be  formed 
from  the  root  to  the  gum  margin  or  from  the  gum  margin  rootward. 

Two  other  phases  of  this  subject  are  of  importance :  one  is  the  color 
of  the  tartar,  the  other  is  the  solubility  of  the  tartar.  Tartar  we  find 
to  be  of  different  colors.  The  tartar  which  forms  rapidly  is  soft  and 
friable,  salivary  in  origin  and  more  nearly  colorless  than  any  of  the 
other  varieties.  It  is  nearer  in  chemical  composition  to  a  simple 
precipitation  of  phosphate  of  lime.  But  when  it  forms  slowly  and 
under  the  margin  of  the  gum  we  usually  find  it  highly  colored.  It 
must  always  be  remembered  that  tartar  precipitated  around  the  necks 
of  the  teeth  is  a  mechanical  irritant  to  the  soft  tissues  of  the  gum 
margin.  This  irritation  predisposes  to  bacterial  infection,  which  leads 
to  an  inflammatory  process  and,  as  the  inflammation  proceeds,  more 
or  less  blood  weeps  out  from  the  irritated  tissue  in  contact  with  the 
tartar.  The  tartar  is  then  colored  by  what  we  call  the  hemoglobin 
or  the  coloring  matter  of  the  red  blood  corpuscles.  In  other  words, 
the  color  of  the  darker  varieties  of  tartar  is  derived  from  the  coloring 
matter  of  the  blood  which  undergoes  a  variety  of  changes  in  color 
when  it  is  subjected  to  the  processes  that  lead  to  its  decomposition. 

It  is  a  familiar  fact  that  a  black  eye,  or  any  black-and-blue  pigmen- 
tation of  the  skin  surface  due  to  a  bruise  is  at  first  red,  then  grows 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  163 

a  little  darker  because  the  coloring  matter  from  the  blood  has  wept 
out  into  the  surrounding  tissues;  then  it  undergoes  chemical  decompo- 
sition, with  a  variety  of  color  changes,  until  it  becomes  very  dark. 
In  the  same  way  when  blood  oozes  out  from  the  gum  margin  and 
comes  in  contact  with  the  tartar  this  coloring  matter  is  absorbed  by 
the  tartar,  becomes  part  of  its  binding  material  and  undergoes  color 
changes  which  are  quite  analogous  to  those  observed  in  a  bruise, 
that  is,  from  a  reddish  or  brown  tint  through  a  variety  of  color  changes 
down  through  brown  and  blue  to  a  final  grayish  or  greenish,  almost 
black,  appearance. 

Tartar  may  be  pigmented  from  other  causes.  It  may  be  pigmented 
through  the  activities  of  certain  bacteria  that  are  color-producing,  or 
it  may  be  pigmented  by  the  character  of  the  food  or  other  material 
that  is  taken  into  the  mouth  as  in  the  case  of  the  betel-nut-chewer, 
or  as  in  the  case  of  tobacco-chewers  or  smokers. 

The  solubility  of  tartar  is  an  important  consideration  from  a  prac- 
tical point  of  view.  We  have  had  to  depend  thus  far  almost  altogether 
upon  mechanical  instrumentation  for  the- removal  of  these  deposits, 
for  the  reason  that  we  have  had  no  proper  solvent  for  this  material, 
something  that  will  disintegrate  it  without  endangering  the  texture  of 
the  teeth.  The  enamel  of  the  teeth  is  composed  of  the  same  mineral 
ingredients  as  tartar,  namely,  calcium  phosphate  and  a  little  carbonate. 
Therefore,  generally  speaking,  a  solvent  of  tartar  will  necessarily  also 
be  a  solvent  of  enamel,  and  it  is  a  very  difficult  proposition  to  apply 
a  solvent  to  the  tartar  without  damaging  the  teeth. 

There  are  instances,  of  course,  where  the  importance  of  the  removal 
of  tartar  in  certain  positions  may  warrant  that  risk,  if  the  solvent  is 
applied  intelligently  and  quickly  neutralized  if  it  tends  to  affect  the 
teeth  detrimentally.  But,  broadly  speaking,  the  chemical  problem  is 
to  find  something  that  will  dissolve  tartar,  but  will  not  dissolve  the 
tooth  structure.  We  would  be  safer  if  we  could  find  some  chemical 
solvent  that  would  dissolve,  not  the  calciimi  phosphate,  but  the 
binding  material  that  holds  the  calcium  phosphate  together,  i.  e.,  the 
mucin;  but  the  calcium  phosphate  is  soluble  in  acid,  while  the  mucin 
is  not.  Mucin  is  soluble  in  alkali  while  calcium  phosphate  is  not 
soluble  in  alkali,  at  least  in  any  such  strength  as  can  be  borne  in  the 
mouth.  So  we  are  confronting  a  very  delicate  problem.  It  is  like 
trying  to  use  a  germicide  strong  enough  to  kill  bacteria  without  killing 
the  individual  that  is  infected  by  them;  to  find  an  agent  selective  in 
its  action,  so  that  it  will  damage  the  germ  and  not  damage  the  host 
of  the  germ. 

Certain  substances  have  been  used  as  tartar  solvents  with  a  fair 
degree  of  success.  Lactic  acid  has  the  property  of  dissolving  the  cal- 
cium phosphate  and  of  forming  soluble  salts  of  calcium  phosphate  and 
may  be  applied  as  a  tartar  solvent.  It  is  not  a  vicious  acid  in  attack- 
ing the  tooth  structure,  and  may  be  applied  to  remove  the  last  par- 
ticles of  tartar  after  the  bulk  has  been  removed  mechanically  by 


164  DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH 

instrumentation.  Solvents  should  not  be  used  for  the  removal  of 
the  bulk  of  tartar  deposits;  they  are  indicated  only  for  the  removal  of 
the  last  remnants.  It  should  never  be  forgotten  that  all  the  other 
pieces  of  tartar  are  of  minor,  even  negligible  importance  as  compared 
with  the  last  piece.  A  man  may  walk  one  hundred  miles  and  take 
many  thousands  of  steps  through  storm  and  weather  to  reach  his 
home,  but  if  he  does  not  take  the  last  step  over  the  doorway,  he  is 
not  home  yet.  He  may  die  before  he  lifts  the  latch.  He  has  not 
reached  his  destination.     All  his  previous  steps  count  for  nothing. 

It  is  quite  the  same  with  reference  to  the  removal  of  deposits.  It 
is  the  last  one  that  counts,  and  when  that  is  removed  the  work  is 
done.  The  last  fragment  of  tartar  sometimes  even  the  most  delicate 
tactile  sense  may  fail  to  detect,  especially  if  it  is  situated  down  toward 
the  end  of  the  root  of  a  tooth,  or  in  a  pocket  which  has  been  thor- 
oughly gone  over  with  the  instrument,  yet  one  is  not  sure  whether  a 
small  particle  has  not  been  left.  It  is  in  such  a  place  that  we  may  have 
recourse  to  the  use  of  a  solvent  such  as  lactic  acid. 

A  word  should  also  be  said  about  the  solubility  of  the  bacterial 
plaque.  As  this  plaque  is  produced  mainly  by  precipitation  of  mucin 
by  acids,  it  is  perfectly  soluble  in  alkalies.  The  alkali  that  is  a  natural 
solvent  of  mucin  precipitated  by  acid  is  calcium  hydroxide,  the  solu- 
tion of  which  we  ordinarily  speak  of  as  lime  water.  A  solution  of 
three  parts  of  lime  water  with  one  part  of  hydrogen  dioxid  has  greater 
efficiency  than  lime  water  as  a  means  of  removing  the  bacterial  plaque. 
The  lime  water  renders  the  mucin  soluble  so  that  it  can  be  washed 
off  the  teeth,  and  the  hydrogen  dioxid  disintegrates  the  plaque,  so 
that  this  solution  has  a  doubly  favorable  action.  It  should  be  used 
habitually  as  a  dentifrice  by  all  patients  who  are  known  to  be  con- 
stitutionally susceptible  to  caries. 

The  sources  of  the  discoloration  of  tartar  to  which  I  referred  are 
also  the  sources  of  the  discolorations  that  we  find  on  teeth,  especially 
in  children,  which  are  spoken  of  as  green  stain  or  brown  stain.  There 
are  two  sources.  The  coloring  matter  of  the  blood  is  the  proteid  sub- 
stance called  hemoglobin.  When  in  solution  in  the  course  of  a  short 
time,  this  color  undergoes  a  change,  becoming  bluish  or  more  purplish 
in  color  as  the  hemoglobin  decomposes.  In  the  course  of  further 
decomposition  it  assumes  a  greenish  tint.  This  color  change  can  be 
effected  much  more  quickly  by  adding  hydrogen  sulphide  to  the  blood. 
Hydrogen  sulphide  is  produced  by  decomposition  of  albuminous 
matter,  as  in  the  decomposition  of  an  egg,  which  then  gives  off  that 
peculiar  odor  of  hydrogen  sulphide,  which  is  due  to  the  decomposition 
of  the  sulphur  elements  in  the  albumin,  and  it  is  the  hydrogen  sulphide 
arising  from  decomposition  of  the  albuminous  or  proteid  elements  of 
the  blood  acting  on  the  hemoglobin  that  changes  its  color  to  a  dirty 
greenish  tint. 

In  cases  of  irritation  of  the  gum  margin,  a  little  of  the  coloring 
matter  of  the  blood  weeps  out,  chemical  changes  go  on  through  the 


DEPOSITS  AND  ACCRETIONS  UPON  THE  TEETH  165 

agency  of  mouth  bacteria,  the  albuminous  portion  of  the  saliva  and 
the  blood  putrefies.  Hydrogen  sulphide  is  given  off,  the  sulphur 
compounds  unite  with  the  coloring  matter  of  the  blood  and  produce 
the  green  or  greenish-brown  stain  observed  on  children's  teeth  and 
the  teeth  of  those  having  irritated  and  bleeding  gums  in  uncleanly 
mouths.  The  chemical  make-up  of  the  pigment  of  that  stain  is  the 
decomposition  product  called  sulphomethemoglobin.  The  children's 
teeth  upon  which  it  is  observed  are  not  properly  kept  clean.  They 
have  a  history  of  lack  of  practical  acquaintance  with  the  toothbrush 
and  the  technic  of  the  ordinary  dental  toilet. 

Another  of  these  green  stains  is  in  all  probability  due  to  pigmenta- 
tions of  the  normal  covering  of  the  enamel  of  the  young  tooth,  which 
we  speak  of  as  Nasmyth's  membrane,  b}'  certain  color-producing  or 
chromogenic  bacteria  bringing  about  that  characteristic  color. 

By  treating  the  young  tooth  with  very  dilute  acids  w^e  can  isolate 
Nasmyth's  membrane  and  examine  it  under  the  microscope,  when  we 
find  it  permeated  with  what  looks  like  the  result  of  bacterial  activity. 

Both  these  types  of  green  stain  upon  the  tooth  surface  are  readily 
removable  by  the  application  of  iodin,  and  the  subsequent  use  of  polish- 
ing powders  or  pumice  applied  on  an  orange-wood  stick.  Iodin  is  not 
only  an  antiseptic,  but  also  a  bleaching  agent.  That  sounds  very 
peculiar,  because  it  stains  of  itself,  but  we  can  stain  the  surface  struc- 
ture of  a  tooth  to  a  deep  tint  with  iodin  and  simply  let  it  alone,  and 
when  the  patient  returns  the  next  day  that  tooth  wdll  be  much  lighter 
in  color,  due  to  the  bleaching  action  of  the  iodin.  We  need  never  be 
afraid  of  permanently  tinting  a  tooth  with  iodin,  unless  w^e  apply  it 
with  a  steel  instrument,  when  iodid  of  iron  is  formed  and  a  permanent 
stain  will  be  produced.  Iodin  itself  nlay  be  used  with  perfect  freedom 
upon  tooth  surfaces  free  from  metallic  fillings  for  the  reason  that  it  is 
ultimately  a  bleaching  agent. 


CHAPTER  VII. 
PYORRHEA  ALVEOLARIS 

By  ARTHUR  H.  MERRITT,  D.D.S. 

Definition  and  History. — Pyorrhea  alveolaris  is  a  disease  affecting  the 
teeth  and  their  investing  tissues.  It  may  be  defined  as  a  progressive 
resorption  of  the  alveolar  process  and  pericementum  with  a  coincident 
shrinkage  and  recession  of  the  gums,  accompanied  by  increasing  loosen- 
ing of  the  teeth.  It  is  a  disease  as  old  as  civilization  and  may  be  older. 
There  is  abundant  evidence  that  it  existed  among  the  early  Egyptians, 
Greeks,  Etruscans,  Phoenicians,  Romans  and  Chinese.  Frequent  men- 
tion is  made  in  their  literature  of  "  loose  teeth,"  "  bleeding  gums,"  etc., 
with  their  discharge  of  "corruption."  Some  attempt  at  treatment  w^as 
made,  usually  in  the  form  of  absurd  mouth  washes,  despite  the  fact 
that  it  was  generally  regarded  as  incurable.  In  this  country  about 
1845,  John  M.  Riggs  of  Hartford,  Conn.,  was  the  first  to  publicly  call 
attention  to  the  disease  and  to  assert  that  it  was  a  curable  disease, 
and  that  by  proper  surgical  treatment  90  per  cent,  of  all  cases  could  be 
cured.  He  achieved  a  considerable  reputation  in  his  generation  and 
was  quoted  at  home  and  abroad  as  an  authority  on  the  subject.  As  a 
result,  the  disease  came  to  be  known  as  "Riggs'  Disease"  though  this 
name  was  not  given  to  it  by  Riggs  himself.  Prior  to  this  it  had  been 
referred  to  as  loose  tooth,  spongy  gums,  scurvy,  etc.  In  1877  F.  H. 
Rehwinkel  gave  to  it  the  name  of  pyorrhea  alveolaris,  in  a  paper  which 
he  read  before  the  American  Dental  Association.  This  name,  which 
was  not  original  with  Rehwinkel,  having  been  borrowed  by  him  from 
European  writers,  has  never  been  wholly  acceptable,  having  been 
severely  criticised  since  its  introduction.  It  means,  literally,  a  flow  of 
pus  from  the  alveolus,  and  is  therefore  descriptive  of  one  phase  only 
in  its  pathology.  Many  attempts  have  since  been  made  to  give  it  a 
more  appropriate  name,  but  without  complete  success;  it  still  remains 
the  name  by  which  it  is  most  generally  known.  For  that  reason  it  is 
used  here,  notwithstanding  the  fact  that  the  name  of  periodontoclasia, 
given  to  it  by  the  American  Academy  of  Periodontology,  is  more  in 
harmony  with  its  pathology  in  its  various  manifestations. 

Pathology .^ — Pyorrhea  alveolaris  is  a  disease  which  begins,  as  a  rule, 
at  the  gingival  border,  and  progresses  slowly  toward  the  apex  of  the 
root,  resulting  in  a  complete  destruction  of  the  alveolar  process  and 
pericementum  with  eventual  loss  of  the  teeth  unless  arrested  by  treat- 
ment. Some  of  the  phenomenon  attending  its  progress  are  gingival 
inflammation,  solution  of  continuity  in  the  floor  of  the  gingival  crevice, 


PATHOLOGY  167 

absorption  of  the  alveolar  process,  pocket  formation,  suppurative 
infection,  sensitiveness  to  thermal  changes,  separation,  elongation  and 
loosening  of  teeth.  Of  these,  the  first  to  manifest  itself  is  gingival 
inflammation  induced  by  various  causes,  the  most  common  of  which  is 
uncleanliness  of  the  mouth.  Irritation  of  the  gingiva  from  any  cause, 
if  long  enough  continued,  results  in  inflammation  which  in  time  may  be 
conveyed  through  the  gingival  group  of  pericemental  fibers  to  the 
pericementum,  eventually  causing  a  break  in  the  floor  of  the  gingival 
crevice.  Coincident  with  this  break,  the  cementum,  pericementum 
and  alveolar  process  are  exposed  to  the  destructive  forces  of  irritation 
and  infection.  A  phenomenon  known  as  halisteresis  is  set  up  in  the 
alveolar  process,  by  which  it  is  slowly  absorbed.  The  rapidity  with 
which  these  changes  occur  will  depend  upon  several  factors — the  thick- 
ness of  the  bone,  the  resistance  of  the  patient,"  the  cleanliness  or  unclean- 
liness of  the  mouth,  etc.  As  a  rule  its  progress  is  slow,  often  many 
years  elapsing  between  the  initial  gingival  irritation  and  final  loss  of 
the  teeth. 

Pyorrhea  alveolaris  manifests  itself  in  a  succession  of  sjonptoms. 
Usually  beginning  as  a  mild  gingival  irritation  which  may  exist  for 
years  without  further  changes,  it  finally  involves  the  subjacent  tissues, 
slowly  destroying  the  pericemental  attachment  at  the  gingivo-enamel 
junction,  absorbing  the  alveolar  crest  and  slowly  advancing  toward  the 
apex  of  the  root,  destroying  the  alveolar  process  and  pericementmn 
as  it  progresses.  This  may  occur  symmetrically  aroimd  the  root,  or, 
as  more  often  happens,  along  one  side  only.  The  destruction  of  the 
alveolar  process  and  pericementum  is  followed  by  shrinkage  and  reces- 
sion of  the  gums,  though  this  recession  never  keeps  pace  with  the  bone 
resorption.  The  result  is  the  formation  of  a  pocket,  bounded  at  one 
point  by  the  extreme  limits  of  bone  necrosis,  and  at  the  other  by  the 
margin  of  the  gum.  The  depth  of  this  pocket  will  depend  upon  the 
amount  of  bone  loss  and  gum  recession.  Laterally  they  are  bounded 
on  the  one  hand  by  the  surrounding  vascular  tissues  and  on  the  other 
by  the  cementum  with  its  investment  of  necrotic  pericementum  and 
calculary  deposit.  Into  these  pockets,  even  in  their  earliest  beginnings, 
the  bacterial  flora  of  the  mouth  finds  its  way.  These  organisms  are 
secondary  invaders  only,  having  no  direct  etiological  relationship  to 
the  disease.  Comparative  studies  of  the  bacterial  flora  of  these 
pockets  show  that  they  do  not  differ  qualitatively  from  that  of  the 
normal  mouth.  There  is,  however,  great  quantitative  difference,  this 
being  explained  by  the  fact  that  these  conditions  are  more  favorable 
to  bacterial  growth  than  are  those  of  the  healthy  mouth.  This  flora  is 
a  mixed  infection  of  great  complexity.  There  is  no  evidence  that  any 
of  these  organisms  sustain  a  direct  causal  relationship  to  the  disease. 
They  are,  however,  responsible  for  one  of  its  characteristic  symptoms  of 
pus  discharge.  These  bacteria  may  also  give  rise  to  secondary  infec- 
tions of  a  serious  nature,  in  many  instances  contributing  to  the  ill 
health  and  inefficiency  of  the  patient,  and  not  infrequently  are  the 


168 


PYORRHEA  ALVEOLARIS 


Figs. 


-1.  iuo.  ad  and  100. — Panoramic  radiographic  view  of  a  normal  denture,  to  show  espe- 
cially the  height  of  the  bony  alveolar  septi  between  the  teeth,  for  comparison  with  other 
radiographs  in  which  destruction  of  the  bone  has  occurred. 


Figs.  101  and  102. — ^Panoramic  radiographic  view  of  the  upper  and  lower  jaw  in  a 
case  of  pyorrhea  of  long  standing.  Note  the  amount  of  bone  that  has  been  destroyed 
by  the  progress  of  the  disease. 


PLATE    VIII 


Fig.  1 


Fig.  2 


Fig.  3 


Fig.  4 


Fig.  5 


Fig.  6 


Cases  of  Gingivitis  and  Incipient  Pyorrhea. 

Note  defective  contact  points,  loss  of  septal  gingiva  and  recession  of  gums;  also  aijscess 
due  to  pyorrhea  in  Fig.  5.     All  caused  by  irritation  from  food  impaction. 


PREVENTION  169 

indirect  cause  of  death.  About  one  thing  there  can  be  no  doubt, 
namely,  their  potentiality  for  evil  is  an  inherent  quality,  dependent 
only  for  its  exercise  upon  the  virulence  of  the  organisms  and  the 
resistance  of  the  patient. 

Etiology. — Pyorrhea  alveolaris  has  a  variety  of  causes,  most  of  which 
have  their  origin  within  the  mouth.  They  have  one  characteristic 
which  is  common  to  them  all  in  that  they  are  irritative  in  their  nature. 
These  causes  may  be  divided  into  two  classes^those  which  begin  at 
the  gingiva  and  by  slow  progression  involve  the  entire  supporting 
tissues  of  the  teeth,  and  secondly  those  which  affect  primarily  the  peri- 
cementum and  alveolar  process.  Of  these  the  more  obvious,  and  also 
the  more  common,  are  those  begining  at  the  gingival  margin  of  the  gimis. 
Anything  which  irritates  the  gingiva  must  be  regarded  as  a  potential 
cause  of  pyorrhea.  Uncleanliness  of  the  mouth,  food  impaction  as  a 
result  of  defective  contact  points,  overhanging  edges  of  fillings,  ill- 
fitting  crowns,  bridges,  etc.,  are  all  causes  of  gingival  irritation.  Of 
these  the  most  common  and  potentially  the  most  dangerous,  is  unclean- 
liness of  the  mouth. 

The  second  form  of  irritation,  that  which  affects  primarily  the  deeper 
periodontal  tissues,  is  traumatic  occlusion.  This  may  be  defined  as  a 
lack  of  harmony  between  the  inclined  planes  of  opposing  teeth  when 
brought  into  occlusion  in  the  act  of  mastication,  as  a  result  of  which 
the  teeth  are  driven  outside  their  normal  limits  of  motion,  and  subjected 
to  a  lateral  strain,  which  if  long  enough  continued,  causes  definite 
changes  in  the  pericementum  and  alveolar  process  with  coincident 
loosening  of  the  teeth.  This  may  exist  in  teeth  with  normal  occlusion 
in  the  usual  meaning  of  the  word,  that  is,  straight  teeth,  and  is  a  very 
common  cause  of  pyorrhea;  it  and  bad  hygiene  being  the  chief  causes. 

It  is  also  possible  that  under  certain  conditions  heredity,  diet,  con- 
stitutional diatheses,  etc.,  may  predispose  to  pyorrhea,  or  may  unfavor- 
ably influence  prognosis.  These  conditions,  however,  are  not  common 
as  shown  by  the  fact  that  most  cases  yield  promptly  to  local  treatment 
when  properly  employed. 

Prevention. — There  are  probably  no  diseases  of  a  chronic  nature 
occurring  in  the  mouth  more  easily  prevented  than  is  pyorrhea  alveo- 
laris, or  none  where  prevention  is  of  more  value.  Its  treatment  in 
advanced  cases  is  always  difficult,  and  the  prognosis  often  doubtful. 
All  such  cases  begin  as  a  simple  lesion,  which  with  all  its  unfortunate 
consequences  might  have  been  prevented  had  proper  care  been  observed. 
As  stated,  this  lesion  usually,  if  not  always,  begins  at  the  gingiva,  caused 
by  some  irritation  of  this  organ,  the  most  common  of  which  is  uncleanli- 
ness of  the  mouth  as  expressed  in  food  accumulations,  tartar,  debris, 
bacteria,  filth,  etc. 

If  a  careful  examination  be  made  of  the  free  gingivae,  it  will  be  found 
that  they  project  themselves  above  the  alveolar  crests  often  to  the 
extent  of  several  millimeters.  Between  the  free  gingiva  and  the 
cervical  enamel  is  the  gingival  crevice,  bounded  at  the  cemento-enamel 


170  PYORRHEA  ALVEOLARIS 

junction  by  the  attachment  of  the  gingival  group  of  pericemental  fibers. 
In  health  the  free  gingivae  terminate  in  a  thin  edge  which  hugs  the 
cervical  enamel  in  such  a  way  as  to  protect  this  pericemental  attach- 
ment against  injury.  If,  as  a  result  of  irritation,  this  knife-like  edge, 
so  admirably  adapted  to  its  purpose,  becomes  inflamed,  its  protective 
property  is  more  or  less  seriously  impaired.  It  no  longer  permits  food 
to  glide  over  it  without  injury  in  the  act  of  mastication,  but  a  certain 
portion  of  it  is  forced  into  the  gingival  crevice,  thereby  adding  to 
the  already  existing  inflammation.  Wherever  inflammation  of  the 
gingivae  exists,  the  quantity  of  the  serum  normally  secreted  into  the 
gingival  crevice  is  increased,  and  if  it  contains  calcoglobulin,  serumal 
calculus  may  be  deposited.  This  deposit,  so  often  found  in  the  gingival 
crevice,  is  not  the  cause,  but  the  efi^ect  of  gingival  irritation,  though  it 
may  in  its  turn  act  as  an  irritant.  The  importance,  therefore,  of  pro- 
tecting the  gingivae  against  irritation  must  be  obvious.  They  stand 
as  protective  barriers  to  the  subjacent  tissues  of  the  teeth,  including 
that  most  vulnerable  point,  the  pericemental  attachment.  Their 
preservation  in  health  is  essential  to  the  proper  function  of  the  teeth; 
to  conserve  and  protect  them  against  injury  is  of  the  first  importance. 
This  is  the  work  to  which  the  dental  hygienist  is  called,  and  there 
is  none  more  worth  while  in  the  whole  field  of  dental  practice.  It  is  a 
service  of  far  more  value  to  the  patient  than  any  restorative  measures 
which  may  be  employed  to  replace  these  teeth  after  they  have  been 
lost,  just  as  preventive  treatment  is  always  of  more  value  than  curative. 
She  has  within  her  power  the  prevention  of  two  of  the  most  common 
diseases  which  afflict  mankind — dental  caries  and  pyorrhea  alveolaris, 
diseases  so  nearly  universal  as  to  affect  all  races  and  all  ages.  The  first 
of  these  can  be  reduced  to  a  minimum  by  oral  hygiene;  the  second  can 
be  almost  completely  prevented  by  the  same  measures.  To  accomplish 
this  the  gingivae  must  be  maintained  in  health;  nothing  must  be  allowed 
to  irritate  them.  Each  gingiva  should  be  carefully  examined  and  the 
slightest  abnormality  in  form  or  color  noted,  and  its  cause  sought  out 
and  removed.  This  cause  will  be  found  to  be  something  which  irri- 
tates— usually  something  acting  from  without,  such  as  an  unclean 
mouth,  defective  contact  points,  which  permit  of  food  impaction, 
overhanging  edges  of  fillings,  crowns,  bridges,  etc.  Certain  chemical 
poisons  acting  from  within,  of  which  mercury  and  potassium  iodide 
are  examples,  may  also  irritate  and  inflame  the  gingivae,  as  may  cer- 
tain poisons  which  result  from  nutritional  disturbances,  but  these  are 
uncommon  and  almost  negligible  factors.  The  really  important  thing 
is  that  they  be  protected  against  external  irritants,  which  is  best 
accomplished  by  thorough  and  painstaking  cleansing  of  the  teeth. 
This  involves  more  than  a  perfunctory  polishing  of  the  enamel  surfaces. 
Every  gingival  crevice  should  be  explored  and  its  contents  removed. 
In  those  cases  in  which  solution  of  continuity  has  taken  place  in  the 
floor  of  the  gingival  crevice,  and  the  subjacent  tissues  have  become 
involved  in  disease,  treatment  by  the  dentist  is  required.    The  more 


SUMMARY  171 

valuable  service  of  prevention  falls  within  the  pro\'ince  of  the  dental 
hygienist. 

Treatment  — Pyorrhea  alveolaris  is  a  curable  disease,  though  it  may 
reach  an  incurable  stage  if  long  enough  neglected.  Its  treatment 
belongs  exclusively  to  the  dentist.  The  dental  hygienist,  however, 
should  be  familiar  with  the  approved  method  of  treatment  and  able 
to  express  an  intelligent  opinion  on  the  subject.  She  can  be  of  great 
assistance  to  the  dentist  in  helping  to  maintain  a  high  degree  of  oral 
cleanliness,  always  a  prerequisite  to  the  best  results.  Its  treatment 
is  essentially  surgical,  a  fact  first  announced  by  Riggs  more  than  three 
quarters  of  a  century  ago.  This  consists  in  the  complete  removal  from 
the  denuded  cementum  of  all  calcareous  deposits,  including  also  the 
necrotic  pericementum.  In  some  instances,  curettage  of  the  affected 
alveolar  process  may  be  necessary.  When  traumatic  occlusion  is 
present,  as  is  often  the  case,  this  must  be  corrected  by  judicious  grind- 
ing of  the  occlusal  surfaces  of  such  teeth.  Treatment  in  advanced 
cases  requires  an  exacting  and  painstaking  technic.  The  absolute 
necessity  of  cleansing  the  involved  cementum  of  all  foreign  and  necrotic 
material,  makes  the  operation  an  exceedingly  difficult  one.  Failure 
in  this  respect  means  unsatisfactory  results,  which  explains  why  it  is 
that  so  many  are  unsuccessful,  and  explains  also  why  so  many  are 
pessimistic  regarding  its  prognosis  and  treatment. 

When,  however,  proper  methods  of  treatment  have  been  employed, 
the  most  gratifying  results  are  achieved.  Health  is  reestablished  in 
the  involved  tissues,  the  teeth  tighten  in  their  sockets,  the  gums  resume 
their  normal  color  and  become  firm  about  the  teeth,  in  some  instances 
reattaching  themselves  to  the  roots,  thereby  completely  obliterating 
the  pockets.  This,  however,  does  not  occur  about  non-vital  teeth 
that  have  become  septic,  nor  about  vital  teeth  upon  which  poor  root 
surgery  has  been  practised. 

Postoperative  treatment  requires  the  maintenance  of  a  high  degree 
of  mouth  cleanliness.  The  patient  must  be  instructed  in  correct 
habits  of  tooth  brushing  and  provided  with  proper  tooth  brushes, 
dentifrices,  waxed  silk  tape,  etc.  This  should  be  supplemented  by 
periodic  cleansing  by  the  dentist  or  hygienist,  the  frequency  of  which 
will  depend  large;ly  upon  the  efficiency  of  the  care  given  by  the  patient; 
three  to  six  months'  intervals  will  be  sufiicient  in  most  cases.  Mouth 
washes,  drugs,  vaccines,  etc.,  have  very  little  place  in  the  prevention 
and  treatment  of  pyorrhea.  Dependence  must  be  placed  upon  normal 
occlusion  and  mouth  hygiene,  not  forgetting  that  anything  which 
irritates  the  gingiva  is  a  potential  cause  of  disease  in  these  tissues. 

Summary. — If  now  a  summary  be  made  of  present-day  knowledge 
regarding  pyorrhea  and  its  treatment,  certain  facts  stand  out  clearly. 
Pyorrhea  is  not,  as  it  is  believed  by  some  to  be,  a  disease  of  modern 
life,  but  is  as  old  as  civilization  itself.  It  expresses  itself  in  many 
forms,  beginning,  as  a  rule,  at  the  gingival  margin,  and  by  extension, 


172  PYORRHEA  ALVEOLARIS 

slowly  involving  all  of  the  supporting  tissues  of  the  teeth,  and  thereby 
causing  their  final  loss. 

Its  causes  are  usually  found  within  the  mouth  itself,  and  may  be 
anything  which  irritates  the  gingivae,  the  most  common  of  which  is 
uncleanliness  of  the  mouth.  It  is  a  disease  which  in  most  instances 
can  be  prevented  when  proper  care  is  observed  by  both  patient  and 
dentist.  To  achieve  this  it  is  essential  that  the  gingivae  be  kept  from 
irritation.  Oral  hygiene  in  its  broadest  sense  is  the  best  means  to  that 
end.  Pyorrhea  is  a  curable  disease  if  taken  in  time.  Its  treatment 
is  surgical  and  depends  for  success  upon  the  thoroughness  and  skill 
with  which  the  operation  is  performed.  As  a  rule,  its  treatment  is 
not  painful.  Mouth  washes  and  drugs  have  no  place  in  treatment. 
This  applies  to  the  hypodermic  use  of  vaccines,  emetin,  etc.  Reliance 
must  always  be  placed  upon  oral  hygiene  in  both  the  prevention  and 
treatment  of  pyorrhea  alveolaris. 


CHAPTER  VIII. 
DENTAL  CARIES. 

By  EDWARD  C.  KIRK,  Sc.D.,  D.D.S.,  LL.D. 

Dental  caries,  or  as  it  is  commonly  designated,  tooth  decay,  is  a  dis- 
ease which,  in  so  far  as  humanity  is  concerned,  is  practically  universal 
in  its  distribution.  It  affects  all  civilized  peoples,  some  uncivilized 
tribes  and,  under  certain  conditions,  even  some  of  the  lower  animals. 
No  disorder  that  afflicts  the  human  race  is  more  common,  as  it  has  been 
shown  by  abundant  statistics  that  from  85  to  95  per  cent,  of  civilized 
human  beings  are  more  or  less  the  victims  of  dental  caries  or  have 
suffered  from  its  ravages  at  some  period  of  their  lives.  Dental  caries 
is  essentially  a  disease  of  childhood  and  adolescence,  the  developing 
individual  appears  to  be  peculiarly  susceptible  to  its  invasion,  whereas 
when  adult  life  is  reached  the  tendency  to  tooth  decay  is  noticeably 
lessened  as  in  the  majority  of  cases  when  the  individual  has  reached 
full  maturity  the  progress  of  tooth  decay  appears  to  be  markedly 
arrested.  So  manifest  are  these  differences  in  the  activity  of  dental 
caries  as  related  to  the  age  and  development  of  the  individual  that  the 
phenomena  of  susceptibility  and  immunity  to  the  disorder  are  accepted 
as  characteristic  of  its  activity.  As  further  evidence  of  the  same 
characteristic  a  small  proportion  of  individuals  are  found  to  be  quite 
free  from  any  evidences  of  tooth  decay,  never  having  suffered  from  its 
invasion  at  any  time  or  in  any  degree,  these  are  regarded  as  being 
naturally  immune. 

The  period  of  childhood  and  adolescence  being  the  period  of  greatest 
susceptibility  to  dental  caries  makes  its  relationship  to  the  health 
of  children  of  school  age  one  of  vital  importance,  not  only  from  the 
hygienic  point  of  view  but  upon  educational  and  economic  grounds 
as  well. 

Comparatively  recent  studies  of  the  question  furnish  abundant  evi- 
dence of  the  fact  that  the  prevalence  of  dental  caries  among  children 
of  school  age  is  the  fruitful  primary  cause  of  mental  backwardness, 
interrupted  brain  development,  nervous  disorders,  errors  of  vision 
and  of  hearing,  bodily  malnutrition  and  a  host  of  evils  which  not 
only  retard  or  interfere  with  the  educational  process  but  impair  to  a 
serious  degree  the  physical  and  mental  efficiency  of  these  developing 
citizens  of  the  future  generation.  Hence  the  importance  of  not 
only  a  proper  understanding  of  the  nature  of  this  important  disorder 
but  a  clear  appreciation  of  its  gravity  as  a  menace  to  human  health 
and  efficiency. 


174 


DENTAL  CARIES 


For  purposes  of  anatomical  description  a  tooth  is  viewed  as  having 
a  crown  (corona)  which  is  all  that  part  of  the  tooth  exposed  beyond 
the  gum,  and  a  root  (radix)  or  radicular  portion  which  is  all  that  part 
of  the  tooth  embedded  in  the  bony  socket  or  alveolus  beneath  the 
gum.  The  portion  at  the  gum  line  between  the  crown  and  the  root 
is  designated  as  the  neck  (cervix)  of  the  tooth. 


Fig.  103. — Vertical  section  of  a  tooth  in  situ  (15  diameters),  c  is  placed  in  the  pulp 
cavity,  opposite  the  cervix  or  neck  of  the  tooth;  the  part  above  is  the  crown,  that 
below  is  the  root  (fang) ;  1,  enamel  with  radial  and  concentric  markings;  2,  dentin  with 
tubules  and  incermental  lines;  3,  cementum,  or  crusta  petrosa,  with  bone  corpuscles; 
4,  pericemental  membrane;  5,  bone  of  mandible. 

Dental  caries  is'  a  destructive  process  affecting  the  hard  dental 
tissues;  these  are  three  in  number:  (1)  The  enamel  which  is  the 
hard  outer  protective  covering  of  the  underlying  dentin  of  the  tooth 
crown  and  (2)  the  cementum  or  crusta  petrosa  covering  the  dentin 


DENTAL  CARIES 


175 


of  the  root;  and  (3)  the  dentin  which  forms  the  principal  body  of  the 
tooth.  Within  the  body  of  the  dentin  in  the  central  cavity  of  the 
tooth  is  located  the  tooth  pulp,  a  soft,  highly  sensitive  and  vascular 
organ,  commonly  but  incorrectly  called  the  "nerve."  From  a  group 
of  specialized  cells  upon  the  surface  of  the  dental  pulp  there  radiate 
through  the  dentin  innumerable  fibers  of  living  matter,  richly  endowed 
with  sensation,  which  with  their  lateral  processes  ramify  throughcmt 
the  dentin  structure.  These  are  termed  the  dentinal  fibers  or  fibrilke, 
and  it  is  through  their  agency  that  we  perceive  the  painful  impres- 
sions arising  from  irritation  of  the  dentin  by  cutting,  by  heat,  cold, 
sweets,  etc. 


Fig.  104. 


-Longitudinal  section  of^dentin,  showing  distribution  of  dentinal  fibers  and 
stratum  granulosum.     (Miller.) 


Dental  caries  always  has  its  inception  upon  the  external  or  exposed 
surface  of  a  tooth;  it  never  arises  from  within  the  tooth.  For  a  long 
period  it  was  held  by  many  students  of  the  subject  that  tooth  decay 
was  an  inflammatory  process  similar  in  certain  respects  to  necrosis  of 
bone,  and  those  who  accepted  that  view  also  held  that  caries  originated 
within  the  tooth  structure  and  gradually  progressed  outwardly  toward 
the  free  enamel  surface.  This  theory  was  maintained  by  some  until 
quite  recent  times,  but  its  fallaciousness  was  finally  completely  demon- 
strated by  the  researches  of  the  late  Prof.  Dr.  W.  D.  Miller,  published 
about  1880,  which  finally  gave  to  the  world  the  true  explanation  of  the 
process  of  tooth  decay. 

Briefly  stated,  Miller,  as  the  result  of  a  long  and  exhaustive  experi- 
mental study  of  the  subject,  found  that  the  destruction  of  the  hard 
structures  of  the  tooth  by  dental  caries  was  accomplished  through 


176  DENTAL  CARIES 

the  agency  of  a  certain  class  of  microorganisms  which  had  the  charac- 
teristic function  of  fermenting  certain  of  the  sugars  and  converting 
these  sugars  into  lactic  acid,  which  acid  in  its  turn  attacked  the  solid 
structure  wherever  it  came  into  contact  with  it,  dissolving  out  its 
mineral  matter  which  caused  the  structure  to  disintegrate,  forming 
a  cavity  which  gradually  enlarged  until  it  eventually  included  the 
entire  crown;  indeed,  if  unchecked,  the  whole  tooth  may  in  this  manner 
become  disintegrated  and  lost. 

A  tooth,  however,  is  not  wholly  composed  of  mineral  matter  soluble 
in  lactic  acid.  If  we  immerse  a  tooth  for  a  sufficient  length  of  time 
in  an  acid,  for  example,  dilute  nitric  or  hydrochloric  acid,  it  will  be 
found  to  have  lost  all  of  its  enamel  covering  and  the  remaining  dentin 
and  cement  structures  while  still  possessing  the  general  conformation 
of  the  original  tooth  will  be  found  to  have  lost  their  hardness  to  such 
a  degree  that  the  structure  may  then  be  easily  cut  with  a  knife  into 
chips  or  slices  like  a  piece  of  cartilage  which  the  structure  now  closely 
resembles.  We  say  of  a  tooth  so  treated  that  it  has  been  decalcified, 
that  is  to  say,  the  calcium  or  lime  salts  which  gave  to  the  tooth 
structure  its  characteristic  hardness  have  been  removed  or  dissolved 
out  by  the  acid  and  what  remains  is  an  organic  substance  or  animal 
tissue  called  the  organic  matrix  or  basis  substance  of  the  dentin  and 
cementum. 

The  relative  proportions  of  calcium  salts  or  mineral  matter  and 
organic  matrix  or  tooth  cartilage  in  the  dentin  and  enamel  structures 
are  shown  in  the  following  analyses: 

Dentin  (Von  Bibra). 

Tooth  cartilage 27.61  \^ 

■p^^  0  40  )  '^^^^^^  matter 

Calcium  phosphate  and  fluoride 66.72) 

Calcium  carbonate 3.36  I  t 

Magnesium  phosphate ^  ^S     Inorganic  matter 

Other  salts 0.83] 

Enamel  (Von  Bibra). 

Cartilage 3.39\r>         •  ^^ 

Fat      .      .      : (J  20  /  °'^''''''=  ""^"^^ 

Calcium  phosphate  and  fluoride 89.82 

Calcium  carbonate 4.37 

Magnesium  phosphate 1 .  34 

Other  salts ■ 0.20 


Inorganic  matter 


Enamel  (Kuehn).  Dentin  (Kuehn). 

CaO 53.75  CaO ^  53.42 

MgO 0.84  MgO 2.41 

P2O6 -37.21  P2O6 39.46 

Fl 0.29  Fl 0.25 

Organic  matter  and  H2O      .        8.48  Organic  matter  and  H2O     .  32.10 

Miller  showed  that  the  first  phase  of  the  carious  process  was  a 
dissolving  out  of  the  mineral  substances  or  decalcification  of  the  tooth 
structure  by  lactic  acid  produced  by  the  ferment  action  of  certain 
microorganisms  on  sugars.     He  further  showed  that  when  decalcifica- 


DENTAL  CARIES  111 

tion  had  taken  place,  infection  of  the  exposed  organic  matrix  of  the 
tooth  structure  by  a  different  type  or  class  of  microorganisms  occurred, 
these  latter  known  as  proteolytic  bacteria,  had  the  power  to  liquefy 
and  bring  about  putrefaction  of  the  organic  matrix  and  to  destroy 
it  in  the  same  manner  that  a  dead  animal  body  is  destroyed  and  disin- 
tegrated by  putrefactive  changes.  These  two  phases  of  the  carious 
process  are  essentially  the  same  in  principle,  dependent  upon  the 
vital  activities  of  microorganisms  of  two  distinct  groups,  each  having 
the  power  to  decompose  certain  compounds  which  enter  into  the 
formation  of  tooth  structure  and  to  produce  by  their  action  certain 
characteristic  physical  phenomena  and  certain  end  or  decomposition 
products  equally  characteristic.  Thus  in  a  cavity  of  decay  the  presence 
of  acid  may  be  easily  demonstrated  by  bringing  into  contact  with  the 
decaying  mass  a  strip  of  blue  litmus  paper  which  will  at  once  turn 
red  where  the  decaying  mass  touches  it.  The  characteristic  odor  of 
putrefaction  is  readily  recognizable,  indeed,  offensively  so,  in  the 
breath  of  those  suffering  actively  from  tooth  decay.  This  odor  of 
putrefaction  arises  in  large  part  from  the  decomposition  of  the  organic 
matter  of  the  dentin  matrix  through  the  agency  of  the  proteolytic 
bacteria. 

The  human  mouth  is  not  only  the  portal  of  entry  for  many  disease- 
producing  microorganisms,  but  because  many  of  these  microscopic 
vegetable  organisms  thrive,  flourish  and  rapidly  reproduce  themselves 
under  the  conditions  of  moisture,  temperature  and  food  supply  that 
they  find  in  the  mouth  cavity  many  species  continue  to  inhabit  the 
mouth  and  those  which  are  possessed  of  disease-producing  charac- 
teristics become  the  agency  of  infection  by  which  a  variety  of  bodily 
diseases  are  produced.  An  unclean  mouth  is  therefore  a  constant 
menace  to  bodily  health  as  well  as  the  ordinary  source  of  tooth  decay. 
Fig.  105  shows  a  mixed  infection  of  various  bacteria  from  a  tooth 
surface. 

But  though  a  great  variety  and  an  almost  infinite  number  of  micro- 
organisms are  constant  inhabitants  of  the  mouth,  and  though  the 
lactic-acid-producing  bacteria  which  cause  tooth  decay  are  found  in 
nearly  all  human  mouths,  it  is  well  known  that  many  teeth  do  not 
decay,  and  even  where  the  decay  process  is  active  not  all  surfaces  of 
the  teeth  are  equally  vulnerable  to  the  process  of  decay. 

It  has  long  been  noticed  that  certain  locations  or  areas  upon  the 
tooth  surfaces  are  more  liable  to  be  the  seat  of  decay  than  are  certain 
other  surface  areas.  In  general,  it  may  be  said  that  those  surfaces  of 
the  teeth  that  are  subjected  to  the  cleansing  action  of  friction  by  the 
tongue,  the  lining  mucous  membrane  of  the  lips  and  cheek  surfaces 
or  teeth  surfaces  which  are  kept  free  of  bacterial  invasion  by  the 
friction  of  rough  or  fibrous  food  materials,  are  less  liable  to  decay; 
whereas,  those  surfaces  of  the  teeth  not  subject  to  the  self-cleansing 
action  of  the  foregoing  causes  are  most  likely  to  be  the  seat  of  decay, 
as  shown  in  Fig.  106. 
12 


17S 


DENTAL  CARIES 


Locations  where  food  particles  infected  by  mouth  bacteria  can  find 
an  undisturbed  lodgement,  such  as  the  natural  pits  and  depressions  in 


Fig.  105. — Mixed  infection  from  tooth  surface.     (Williams.) 


Fig.  106. — Caries  localized  above  the  "contact  point"  on  the  approximating  surfaces  of 
contiguous  molar  teeth.      (Williams.) 

the  masticating  surfaces  of  the  molars  and  premolars,  the  sulci  between 
the  cusps,  and  especially  the  approximating  surfaces  of  the  teeth  which 
by  their  mutual  relations  of  contact  afford  protected  areas  for  the 


DENTAL  CARIES 


179 


lodgement  of  food  particles  and  its  undisturbed  decomposition  by 
lactic-acid-producing  bacteria  are  areas  which  in  a  susceptible  individ- 
ual are  the  selected  locations  of  the  carious  process  (Figs.  107  and  108). 


Fig.   107.- 


-Beginning  caries  in  sulci  and  enamel  defects  of  morsal  surface  of  a  molar, 
also  showing  transparent  zone  of  Tomes.     (Miller.) 


Fig.  108. — Beginning  caries  on  approximal  surface.     (Miller.) 

The  determination  of  the  location  of  tooth  decay  is  in  large  degree 
a  result  of  the  form  of  the  individual  tooth  and  of  the  relations  of  the 
teeth  to  each  other  in  the  dental  arches. 


180  DENTAL  CARIES 

The  structure  of  the  tooth  itself,  that  is  to  say,  whether  it  be  hard 
and  dense  or  whether  it  be  relatively  soft  and  imperfectly  calcified, 
does  not  in  the  slightest  degree  influence  the  liability  of  teeth  to  decay 
or  otherwise.  Any  tooth  will  decay  in  a  mouth  where  the  conditions 
causing  decay  are  active  and  no  tooth  will  decay  whatever  its  structure 
may  be  in  a  mouth  where  the  conditions  causing  decay  are  not  active. 
Or,  as  stated  by  the  late  Prof.  G.  V.  Black,  "decay  of  the  teeth  is  a 
factor  of  the  environment  of  the  teeth.  It  is  not  due  to  the  structure 
of  the  teeth  in  so  far  as  their  structure  is  characterized  by  density, 
hardness,  softness,  etc.  These  factors  may  influence  the  rate  of  decay 
but  they  do  not  determine  the  liability  to  decay." 

When  starchy  food  particles,  sugars  or  any  form  of  fermentable 
carbohydrate  food  material  is  lodged  in  contact  with  a  protected  area 
of  tooth  surface  it  becomes  subject  to  the  action  of  lactic-acid-produc- 
ing microorganisms  and  undergoes  fermentation  resulting  in  its  decom- 
position with  the  production  of  lactic  acid.  A  familiar  example  of  this 
process  is  the  souring  of  milk  when  left  exposed  for  a  time  to  the  air 
at  a  warm  room  temperature.  Milk  contains  a  considerable  quantity 
of  a  characteristic  sugar  called  sugar  of  milk  and  chemically  desig- 
nated lactose,  having  the  formula  C6H12O6.  Bacteria  from  the  air 
fall  into  the  milk  and  set  up  a  fermentation  of  the  milk  sugar  decom- 
posing it  or  splitting  it  into  lactic  acid  which  when  it  accumulates 
sufficiently,  gives  the  milk  an  acid  reaction  and  a  sour  taste.  The 
acid  thus  formed  breaks  up  the  combination  of  the  casein  with  the 
base  with  which  it  was  in  chemical  union  and  precipitates  the  casein 
as  a  curd  so  that  the  milk  becomes  thickened  and  when  separated  from 
its  watery  whey,  this  curd  is  the  material  from  which  cheese  is  made. 

The  casein  or  cheesy  portion  of  the  milk  will  also  undergo  putre- 
factive changes  through  the  agency  of  proteolytic  and  other  forms  of 
bacteria  which  have  the  property  of  decomposing  this  type  of  organic 
matter  so  that  the  process  of  fermentation  and  subsequent  putre- 
faction of  milk  is,  in  principle  at  least,  quite  analogous  to  the  process 
of  tooth  decay. 

The  conversion  of  sugar  into  lactic  acid  by  the  fermentative  agency 
of  bacteria  is  represented  by  a  chemical  formula  as  follows : 

Glucose.  Lactic  acid. 

C6H12O6  +  the  enzyme  of  B.  acidi  lactici  =  2C3H6O3 

that  is  to  say,  a  molecule  of  the  monosaccharid  glucose  is,  under  the 
action  of  the  enzyme  of  the  B.  acidi  lactici,  split  up  into  two  molecules 
of  lactic  acid.  Starches,  cane  sugar  and  the  more  complex  carbohy- 
drates must  first  undergo  changes  in  the  mouth  into  the  simpler  forms 
like  glucose  before  they  can  be  split  into  lactic  acid  and  these  pre- 
liminary changes  are  brought  about  by  other  enzymes,  and  particu- 
larly by  ptyalin,  the  characteristic  ferment  of  the  saliva  which  pos- 
sesses marked  amylolytic  properties  or  the  power  to  convert  starches 
into  sugars  that  may  be  subsequently  split  into  lactic  acid  by  the 
agency  of  the  proper  bacterial  enzyme. 


DENTAL  CARIES  181 

These  chemical  alterations  as  the  result  of  the  action  of  digestive 
ferments  and  bacterial  enzymes  upon  the  debris  of  food  substances 
are  constantly  going  on  in  mouths  which  are  not  kept  clean  and  free 
from  food  remnants  either  by  habitual  use  of  the  usual  tooth-cleansing 
devices  of  brush  and  dentifices,  unless  we  may  exclude  those  excep- 
tional cases  which  are  naturally  self-cleansing  and  therefore  immune. 
It  is  this  constant  fermentative  activity  that  initiates  dental  caries 
wherever  on  a  localized  area  of  tooth  structure  it  is  permitted  to  con- 
tinue undisturbed. 

It  should  be  borne  in  mind  that  dental  caries  is  a  distinctly  localized 
process  in  its  inception.  The  disease  may  appear  in  one  or  many 
places  in  the  same  mouth,  at  the  same  time,  but  it  is  localized  in  the 
sense  that  it  does  not  attack  all  surfaces  of  the  teeth  simultaneously, 
nor  with  equal  impartiality.  Many  who  in  the  beginning  of  their 
study  of  the  pathology  of  dental  caries  have  clearly  grasped  the  fact 
that  lactic  acid  is  the  agent  which  initiates  the  disorder  by  dissolving 
out  the  lime  salts  of  a  localized  area  of  tooth  structure,  and  that  the 
first  stage  of  cavity  formation  is  thus  explained,  not  infrequently 
jump  to  the  erroneous  conclusion  that  lactic  acid  alone  is  the  cause 
of  tooth  decay  and  cavity  formation. 

As  a  matter  of  fact,  a  generally  acid  saliva,  even  if  the  acidity  be 
due  to  lactic  acid,  will  not  give  rise  to  tooth  decay.  An  acid  saliva  is 
destructive  of  tooth  structure  by  bringing  about  a  general  decalcifica- 
tion of  the  teeth  which  is  manifested  more  intensely  in  certain  locations 
than  in  others,  but  this  type  of  destruction  of  tooth  structure  is  not 
dental  caries  but  what  is  called  chemical  erosion  of  the  teeth,  a  disorder 
not  necessarily  dependent  upon  bacterial  activity,  as  it  may  be  pro- 
duced by  any  free  acid  formed  in  the  mouth,  exuded  into  the  mouth, 
or  taken  into  the  mouth. 

Dental  caries  is  a  characteristic  disease  with  a  well-marked  and 
definite  group  of  symptoms  and  within  certain  limits  it  has  a  known 
causation,  which  is  the  localized  destruction  of  the  hard  tissues  of  the 
tooth  by  the  solvent  action  of  lactic  acid  generated  at  the  point  of 
decay  by  the  agency  of  bacteria  acting  upon  carbohydrate  foodstuff. 

While  localization  of  the  decay  process  is  to  a  large  degree  deter- 
mined by  the  forms  of  the  teeth  and  their  relations  to  each  other, 
as  already  explained,  there  is  another  and  somewhat  complicated 
method  by  which  fixation  of  lactic-acid-producing  bacteria  to  a  tooth 
surface  is  brought  about,  a  method  which  because  of  its  importance 
in  relation  to  oral  hygiene  as  well  as  to  the  causation  of  decay  should 
be  clearly  understood  and  that  is  the  localization  of  decay-producing 
bacteria  upon  the  tooth  surfaces  by  the  precipitation  of  mucic  acid 
from  the  mucin  of  the  saliva  by  the  lactic  acid  set  free  by  the  activity 
of  the  bacteria  themselves. 

The  precipitation  of  the  mucic  acid  upon  tooth  surfaces  is  dis- 
cussed in  detail  in  the  chapter  on  Deposits  Upon  the  Teeth,  as  it  is 
a  result  of  bacterial  activity  responsible  to  a  considerable  degree 


1S2  DENTAL  CARIES 

for  the  formation  of  those  adhesive  deposits  upon  the  teeth  to  which 
the  general  designation  of  tartar  is  applied;  it  is  important  to  recapitu- 
late its  main  features  here  in  so  far  as  they  are  concerned  in  localizing 
the  process  of  dental  caries. 

In  mouths  where  caries  is  in  active  progress  the  saliva  is  ordinarily 
rich  in  mucin  which  when  present  in  appreciable  quantities,  is  recog- 
nizable by  the  glairy  or  ropy,  adhesive  character  of  the  fluid.  The 
saliva  has  the  property  of  viscosity;  it  has  a  certain  cohesiveness  and 
may  be  drawn  out  into  threads  of  greater  or  less  length  according  to 
the  quantity  of  mucin  that  it  holds  in  solution.  Such  saliva  is  nearly 
neutral  or  faintly  alkaline  in  reaction.  If  to  a  small  quantity  of  such 
a  saliva  gathered  in  a  test-tube  a  drop  of  lactic  acid,  or,  indeed,  any 
acid  is  added,  there  will  be  formed  at  the  point  of  contact  an  opales- 
cent precipitate  which  is  the  mucic  acid  set  free  from  the  alkaline  base 
with  which  it  was  previously  in  chemical  combination  in  the  saliva 
as  mucin. 

If  the  test-tube  is  allowed  to  stand  undisturbed  for  some  minutes 
the  precipitate  will  settle  to  the  bottom  of  the  glass.  The  precipitated 
mucic  acid  is  adhesive  and  insoluble  except  in  an  alkaline  or  saline 
solution.  If  now  we  apply  these  data  to  our  study  of  what  takes 
place  in  the  mouth,  we  shall  find  that  they  throw  much  light  upon 
the  mode  of  localization  of  the  carious  process. 

Assuming  that  in  a  susceptible  mouth  the  saliva  is  rich  in  mucin 
held  in  solution  by  the  alkaline  salts  of  the  saliva  and  that  the  mouth 
contains  carbohydrate  food  material  in  the  form  of  soluble  sugars, 
produced  by  the  amylolytic  action  of  the  salivary  ferment  ptyalin 
upon  starchy  food  debris,  then,  in  such  a  mouth  infected  by  lactic- 
acid-producing  bacteria,  one  or  more  of  these  organisms  falling  upon 
a  tooth  and  temporarily  lodged  in  some  irregularity  of  the  enamel 
surface,  immediately  sets  up  a  fermentative  action  in  the  soluble 
sugar  of  its  salivary  environment  setting  free  lactic  acid  in  the  imme- 
diate vicinity  of  the  bacterium.  The  liberated  acid  at  once  decomposes 
the  dissolved  mucin  of  the  saliva  throwing  down  the  adhesive  mucic 
acid  in  contact  with  the  body  of  the  microorganism,  cementing  it,  as  it 
were,  to  its  position  upon  the  enamel  surface.  Multiplication  of  the 
bacteria  proceeds  rapidly  and  the  process  of  acid  production  and  mucic 
acid  precipitation  proceeds  in  harmony  with  the  bacterial  multiplica- 
tion. The  mass  of  bacteria  thus  organized  and  cemented  to  the  tooth 
surface  constitutes  what  is  known  as  a  bacterial  plaque,  the  essential 
factor  in  the  localization  of  tooth  decay  and  the  most  important  charac- 
teristic in  the  causation  of  the  disease.     (See  Fig.  109.) 

The  bacterial  plaque  presents  a  variety  of  physical  appearances 
under  the  microscope.  It  may  exist  as  a  small  glistening  semitrans- 
parent  mass  occupying  only  a  small  spot  of  the  enamel  surface  or  it 
may  present  the  appearance  of  a  film  extending  over  a  considerable 
area,  in  fact,  over  all  surfaces  of  the  tooth  not  subject  to  friction  by 
food  or  the  tongue  and  buccal  mucous  surfaces.    The  microorganisms 


DEl^TAL  CARIES 


m 


found  in  the  plaque  are  never  a  pure  culture  of  lactic-acid  producers 
but  while  these  are  presumably  always  present,  the  organisms  are 
usually  those  constituting  the  mixed  infection  usually  found  in  the 
unclean  mouth  (Fig.  105). 

It  has  been  shown  that  tooth  decay  is  brought  about  in  the  first 
place  by  the  decalcifying  action  of  lactic  acid  produced  by  the  ferment 
action  of  bacteria  upon  carbohydrate  food  debris.  This  is,  however, 
a  general  statement  of  fact  that  requires  somewhat  closer  analysis  in 
order  that  the  exact  nature  of  the  process  may  be  more  clearly  under- 
stood. All  carbohydrate  material  is  not  directly  fermentable  into 
lactic  acid,  thus  cane  sugar  and  starches,  two  important  nutritive 
substances,  must  undergo  certain  chemical  changes  in  the  mouth 
by  which  they  are  converted  into  simple  forms  of  sugar,  the  mono- 


FiG.  109. — Bacterial  plaque,  detached  from  enamel  sxirface  of  the  tooth  in  making  the 
preparation.     (Williams.) 


saccharids  having  the  general  formula  CeHiaOe,  before  the  bacteria  of 
tooth  decay  can  convert  them  into  lactic  acid,  this  preliminary  change 
called  hydration  or  hydrolysis,  is  brought  about  in  the  case  of  starches 
by  the  ferment  ptyalin,  an  enzyme  produced  by  the  salivary  glands 
and  which  is  therefore  a  normal  constituent  of  the  saliva.  Its  func- 
tion is  to  prepare  the  starches  and  possibly  some  of  the  more  complex 
sugars  for  later  assimilation  by  the  cells  of  the  body  in  the  process 
of  nutrition. 

The  physiological  chemist  Claude  Bernard  showed  by  experiment 
that  cane  sugar  as  such  is  not  assimilated  by  the  human  organism  when 
injected  into  the  veins,  but  when  taken  into  the  mouth  is  later  acted 
upon  by  a  special  amylolytic  enzyme  called  invertase  in  the  intestinal 
canal  and  thereby  converted  into  a  monosaccharid  assimilable  sugar 
suitable  for  the  nutrient  purposes  of  the  organism. 


184  -  DENTAL  CARIES 

The  typical  conversion  of  starch  and  of  cane  sugar  respectively  into 
lactic  acid  may  be  shown  chemically  as  follows : 

Cane  sugar.  : 

Cl2H?20ll      "l"     H2O 

becomes  hydrolyzed  through  the  action  of  invertase  to 

Glucose. 

Cl2H240l2      =      2C6Hl206 

which  through  the  enzyme  action  of  B.  acidi  lactici  is  split  into 

Lactic  acid. 
4C3H6O3 

and 

Starch. 
C12H20O10    -\-    2H2O 

becomes  hydrolyzed  and  starch  through  the  action  of  diastase,  or 
ptyalin,  to 

Glucose. 
C12H24O12    =    2C6H12O6 

which  through  the  enzyme  action  of  B.  lactici  is  likewise  split  into 

Lactic  acid 
4C3H6O3 

From  the  foregoing  it  will  be  seen  that  the  mother  substance  from 
which  mouth  bacteria  produce  lactic  acid  is  a  simple  form  of  sugar 
belonging  to  the  monosaccharid  group  of  sugars  called  the  hexoses 
from  their  chemical  constitution,  all  having  the  formula  C6H12O6,  a 
compound  which  readily  splits  into  two  molecules  of  lactic  acid  having 
the  formula  2C3H6O3.  The  sugars  being  soluble  substances  readily 
diffuse  into  or  are  capable  of  absorption  by  the  bacterial  plaque  so 
that  the  bacteria  thus  fixed  and  localized  upon  a  protected  tooth  sur- 
face are  nourished  by  a  food  supply  of  soluble  sugar  directly  convert- 
ible into  lactic  acid  which  being  produced  continually  in  these  localized 
areas  of  bacterial  fixation  exerts  its  solvent  and  decalcifying  action 
upon  the  enamel  without  interference. 

The  manner  in  which  enamel  disintegrates  under  the  solvent  action 
of  lactic  acid  is  both  interesting  and  important.  The  enamel  covering 
of  a  tooth  crown  is  made  up  of  innumerable  prismatic  rods  or  prisms 
irregularly  hexagonal  in  section  and  densely  calcified.  These  enamel 
prisms  stand  endwise  to  the  dentin  and  pursue  a  radiating  and  some- 
times wavy  course  to  the  periphery  or  free  enamel  surface.  The  prisms 
are  bound  together  by  a  material  of  much  the  same  chemical  nature 
as  that  constituting  the  prisms  themselves,  but  it  differs  therefrom 
in  the  physical  sense  that  it  is  more  readily  soluble  in  acids.  If  we 
take  a  thinly  ground  section  of  enamel  and  place  it  on  a  slide  and 
while  examining  it  under  the  microscope  allow  a  drop  or  two  of  dilute 
acid  to  act  upon  the  free  edge  of  the  specimen,  we  will  see  that  the 
acid  dissolves  out  the  interprismatic  cementing  substance  much  more 
rapidly  than  it  affects  the  structure  of  the  prisms  themselves;  hence 


DENTAL  CARIES 


185 


the  acid,  because  of  this  greater  solubility  of  the  interprismatic  cement- 
ing substance,  tends  to  penetrate  between  the  prisms  separating  them 
from  each  other  and  causing  them  to  fall  apart  as  shown  in  Fig.  110. 
It  is  precisely  this  effect  that  we  see  in  the  opaque  chalky  white 
spots  that  make  their  appearance  upon  susceptible  tooth  areas  and 
which  the  intelligent  operator  recognizes  as  the  beginning  of  dental 
decay.  The  opacity  and  chalky  appearance  of  these  spots  is  due  to 
the  fact  that  the  interprismatic  cementing  substance  that  formerly 
gave  the  appearance  of  homogeneity  to  the  enamel  structure  has  been 
dissolved  out  leaving  air  or  fluid  in  its  place  having  a  different  refrac- 
tive index  than  the  enamel  (Fig.  111).  As  the  process  proceeds  the 
area  enlarges  and  the  enamel  rods  having  lost  the  means  of  mutual 
support,  fall  apart  and  are  lost,  leaving  an  open  cavity  in  their  former 
location. 


Fig.  110. — Section  of  enamel  subjected  to  the  action  of  dilute  acid,  showing  solvent 
effect  on  the  interprismatic  cementing  substance  and  penetration  of  the  acid  between 
the  enamel  rods.     (Williams.) 

The  irritative  effect  of  the  gradual  penetration  of  acid  through  the 
enamel  in  the  process  of  tooth  decay  is  manifest  at  a  very  early  stage. 
Even  before  an  actual  cavity  has  been  formed  or  the  acid  penetration 
has  reached  the  junction  of  the  enamel  with  the  dentin,  the  latter 
tissue  will  have  manifested  its  reaction  to  the  irritation  by  recording 
certain  characteristic  changes  in  its  structure.  In  a  section  of  a  tooth 
attacked  by  slowly  advancing  caries  there  will  be  noticed  in  the 
structure  of  the  dentin  lying  subjacent  to  the  line  of  invasion  a  cone- 
shaped  area  between  the  dentino-enamel  border  and  the  pulp  cavity 
with  the  apex  of  the  cone  toward  the  pulp  and  the  base  toward  the 
disintegrating  enamel.  This  cone-shaped  area  of  dentin  is  more  trans- 
parent than  the  surrounding  dentin  structure  and  from  its  peculiar 
transparency  has  been  called  the  transparent  zone  of  Tomes,  from  Sir 
John  Tomes,  who  first  described  it.  Various  theories  as  to  the  cause 
of  this  alteration  in  the  character  of  the  dentin  structure  have  been 


1S6  DENTAL  CARIES 

advanced,  and  such  authorities  as  Tomes,  Magitot,  Miller  and  Walkhoff 
regard  it  as  being  an  overcalcification  of  the  dentin  structure  as  a  result 
of  the  irritation  of  the  living  matter  of  the  dentin.  Certain  it  is  that  it 
is  the  expression  of  a  vital  reaction  upon  the  part  of  the  dentin,  for  it 
does  not  occur  in  dead  (i.  e.,  pulpless)  teeth  and  it  always  does  occur 
from  long-continued  slight  irritation  to  the  dentin  from  whatever 
cause.  Its  main  importance  in  connection  with  the  study  of  dental 
caries  is  that  it  records  indisputably  the  fact  that  dental  caries  in 
its  progress  sets  up  irritation  which  is  felt  and  recorded  by  the  vital 
elements  of  the  tooth,  even  in  the  earliest  stages  of  the  disease  and 
before  the  integrity  of  the  enamel  surface  has  as  yet  been  seriously 
disturbed  (see  Fig.  107,  a). 

CARIES  OF  DENTIN. 

When  the  enamel  has  been  penetrated  and  a  cavity  has  thus  been 
formed,  invasion  of  the  dentin  rapidly  follows.  Caries  of  the  dentin 
differs  from  caries  of  enamel  in  two  important  particulars  arising  out 
of  the  differences  in  structure  and  composition  of  the  dentin  as  com- 
pared with  that  of  the  enamel. 

The  dentin  contains  a  relatively  larger  amount  of  organic  matter  than 
the  enamel;  the  earthy  salts  entering  into  the  composition  of  the  dentin 
are  deposited  in  a  cartilaginous  substance  having  the  general  form  of 
the  tooth  and  known  as  the  organic  matrix  or  basis  substance  of  the 
dentin.  The  organic  matrix  which  in  the  formed  tooth  is  fully  calcified 
is  everywhere  permeated  by  fibrils  of  sensitive  living  matter  encased 
in  tubules  which  radiate  from  the  surface  of  the  pulp  through  the 
dentin  structure.  It  is  these  fibrils  of  living  matter  that  endow  the 
dentin  with  sensation  and  which  give  rise  to  pain  when  the  dentin 
is  cut  as  in  the  preparation  of  a  cavity  of  decay  preparatory  to  the 
filling  operation  or  when  sweets,  acids  or  other  irritating  substances 
are  brought  into  contact  with  the  walls  of  a  carious  cavity. 

The  distribution  of  living  matter  in  the  dentin  may  be  seen  from 
Fig.  104,  which  is  reproduced  from  a  photograph  of  a  section  of  the 
dentin  cut  in  the  plane  of  the  long  axis  of  the  tubules  in  which  the 
fibrillse  run. 

As  soon  as  loss  of  enamel  exposes  the  ends  of  the  dentinal  fibrillse 
invasion  of  the  tubules  by  the  bacteria  of  decay  promptly  takes 
place  and  the  tendency  of  the  carious  process  is  to  follow  the  direction 
of  the  tubules  toward  the  dental  pulp. 

Within  the  dentinal  tubule  the  bacteria  of  decay  elaborate  their 
characteristic  lactic  acid  which  dissolves  the  sides  of  the  tubule  enlarg- 
ing its  diameter,  the  increased  space  being  promptly  packed  with 
organisms  reproduced  from  the  parent  pioneers  of  the  invasion  the 
dissolution  of  the  tubular  walls  continuing  until  the  area  of  decalcifica- 
tion involves  adjacent  tubules  which  have  been  undergoing  a  similar 
process  of  enlargement  until  coalescence  of  a  number  of  tubes  takes 


CARIES  OF  DENTIN 


187 


place  (Figs.  112  and  113).     Coincidently,  as  decalcification  proceeds 
and  exposure  of  the  organic  nnatrix  occurs,  that  structure  is  attacked  by 


Fig.  111. — Section  of  tooth,  showing  localized  solution  of  interprismatic  cement 
substance  with  enamel  rods  standing,  constituting  the  "opaque  spot"  of  beginning 
decay.     (Miller.) 


Fig.  112. — Longitudinal  section  of  carious  dentin,  showing  enlarged  tubules  packed  with 

bacteria.     (Miller.) 


a  group  of  bacteria  known  as  proteolytic  organisms  which  have  the 
property  of  elaborating  an  enzyme  that  brings  about  liquefaction  of 


188 


DENTAL  CARIES 


the  cartilaginous  proteid  material  constituting  the  organic  matrix. 
Decomposition  and  putrefaction  of  the  decalcified  basis  substance  of 


Fig.  113. — Cross-section  of  carious  dentin,  showing  enlarged  tubules.     (Miller.) 


Fig.  114. — Liquefaction  foci  in  carious  dentin.     (Miller.) 


the  dentin  thus  takes  place  with  the  formation  of  so-called  liquefac- 
tion foci  in  the  dentin  which  liquefaction  foci  by  their  extension  and 
coalescence  ultimately  produce  what  is  commonly  known  as  a  cavity 


CARIES  OF  DENTIN  189 

of  tooth  decay,  the  process  continuing  until  the  pulp  is  reached  or, 
if  the  process  is  not  arrested,  until  the  tooth  is  destroyed  (Fig.  114). 

It  has  already  been  noted  that  invasion  of  the  dentin  by  the  bac- 
teria of  caries  is  by  way  of  the  dentinal  tubules  which  these  organisms, 
generally  speaking,  follow  toward  the  pulp  and  various  considerations 
seem  to  indicate  that  this  mode  of  invasion  of  the  dentin  is  largely 
determined  by  the  fact  that  the  source  of  food  upon  which  the  organ- 
isms feed  is  found  in  the  substance  of  the  dentinal  fibril  or  the  juices 
of  the  fibril  itself. 

It  has  been  clearly  demonstrated  by  the  researches  of  Miller, 
already  referred  to  and  confirmed  by  other  able  and  trustworthy 
investigators,  that  dental  caries  can  be,  and  is,  due  to  decomposition 
of  carbohydrate  food  particles  in  unclean  mouths,  fro;m  which  we  have 
drawn  the  conclusion  that  tooth  decay  is  a  filth  disease,  that  if  proper 
care  as  to  oral  hygiene  is  instituted  and  maintained  dental  caries  may 
be  eradicated;  in  short,  we  have  come  to  regard  it  as  an  accepted 
fact  that  "clean  teeth  will  not  decay.''  This  conclusion  is  probably 
too  hastily  drawn  and  without  full  consideration  of  all  the  factors 
involved,  which  tend  to  limit  its  general  application. 

Experience  shows  that  teeth  decay  more  rapidly  in  early  than  in 
adult  life,  that  the  teeth  of  some  individuals  decay  more  rapidly  than 
others,  that  the  teeth  of  some  never  decay,  that  many  who  give  scrupu- 
lous attention  to  their  teeth  are  extremely  susceptible  to  decay  of  the 
teeth,  while  others  whose  mouths  never  receive  any  attention  appear 
to  be  immune. 

The  problems  of  susceptibility  and  immunity  to  dental  caries  are 
as  yet  unsolved;  there  are,  however,  many  indications  that  give  color 
to  the  hypothesis  that  there  are  certain  nutritional  factors  that  have 
much  to  do  with  the  susceptibility  to  dental  caries  or  with  immunity 
therefrom.  Those  who  live  upon  an  excessive  carbohydrate  diet  are, 
as  a  rule,  found  to  be  more  prone  to  carious  invasion  than  those  whose 
diet  is  largely  of  a  proteid  character.  Probably  under  an  excessive 
carbohydrate  diet  the  percentage  of  sugar  in  the  blood,  normally  about 
0.001,  is  increased  and  if  the  salivary  fluids  and  the  juices  of  the  dentinal 
fibrils  derived  from  the  blood  reflect  this  increase  in  carbohydrate 
above  the  physiological  normal  would  readily  invite  the  invasion  of 
decay-producing  bacteria.  In  1881  Milles  and  Underwood  expressed 
the  opinion  that  the  bacteria  feed  upon  the  juices  of  the  dentinal 
fibrillse  in  dental  caries  as  follows :  "  The  organic  fibrils  upon  which  the 
organisms  feed  and  in  which  they  multiply  are  the  scene  of  the  manu- 
facture of  their  characteristic  acids,  which  in  turn  decalcify  the  matrix 
and  discolor  the  whole  mass."^ 

If,  then,  susceptibility  to  tooth  decay  is  in  considerable  degree 
dependent  upon  a  constitutional  predisposition,  oral  hygiene  alone  and 
unaided  cannot  wholly  prevent  it,  although  it  can  undoubtedly  greatly 

1  Trans.  Seventh  International  Congress  of  Medicine,  London,  1881. 


190  DENTAL  CARIES 

diminish  its  ravages.  It  is  highly  probable  from  our  present  knowl- 
edge of  the  subject  that  complete  control  of  this  universal  disorder 
can  never  be  attained  by  local  measures  alone.  The  fundamentally 
important  question  of  dietetics,  of  food  habit,  must  be  studied  for 
what  light  it  can  throw  on  the  solution  of  the  problem,  for  even  now  the 
evidence  is  almost  overwhelming  that  the  inordinate  and  increasing 
habitual  use  of  sweets  by  civilized  children  is  a  custom  pernicious 
alike  to  the  integrity  of  their  dentures  and  to  their  general  health. 

Until  the  deeper  underlying  factors  of  the  causation  of  dental  caries 
are  discovered  we  must  rely  upon  the  means  at  our  command  in 
the  principles  and  art  of  oral  hygiene  to  protect  humanity  as  best  we 
may  from  the  scourge  of  dental  caries  and  its  consequent  damage  to 
health  and  life. 


CHAPTER  IX. 
ODONTALGIA  AND  NEURALGIA. 

By  ARTHUR  HOPEWELL-SMITH,  Sc.D.,  L.R.C.P.,  M.R.C.S.,  L.D.S. 

Introductory. — The  word  odontalgia  is  a  pure  Greek  derivative, 
meaning  literally  "tooth  pain."  It  is  popularly  spoken  of  as  "tooth- 
ache." But  the  latter  term  possesses  another  and  more  significant 
meaning  which  the  popular  imagination  and  experience  cannot  dis- 
tinguish from  pain  in  a  tooth;  it  includes  also  neuralgia,  the  English 
form  of  two  Greek  words  which  indicate  "  nerve  pain."  It  thus  happens 
that  odontalgia  and  neuralgia  are  frequenth'  mistaken  for  each  other. 
Further,  it  frequently  happens  clinically,  that  both  occur  simultane- 
ously, thus  rendering  the  pathological  conditions  which  induce  them 
obscure  and  difficult  to  determine. 

It  is  the  purpose  of  this  chapter  to  set  forth  in  a  simple  fashion 
an  account  of  the  two  chief  types  of  pain  associated  with  the  dental 
organs  of  man. 

ODONTALGIA. 

Odontalgia  is  not  a  disease,  but  a  symptom  or  sign  of  a  disease  or 
diseases.  Neuralgia,  similarly,  except  for  the  very  specific  condition 
called  epileptiform  neuralgia,  is  a  sjonptom.  Pain  itself  cannot  be  a 
morbid  state  of  the  body.  It  is  an  indicator — a  beneficent  indicator 
of  a  diseased  condition  of  an  organ,  due  to  a  disturbance  of  the  sensory 
nervous  mechanism  of  that  organ.  A  tissue  or  organ  devoid  of  sensory 
nerves  is  incapable  of  feeling  pain  locally,  as  exemplified,  for  instance, 
in  the  liver.  On  the  other  hand,  an  organ  freely  supplied  with  sense 
filaments  is  exceedingly  subject  to  pain,  as  exemplified  in  the  dental 
pulp  where  the  nerve  fibers  are  partly  sensory  and  partly  sympathetic 
—that  is,  distributed  to  and  thus  control  the  blood  vascular  system. 

It  therefore  follows  that  odontalgia  is  a  common,  special,  important, 
and  distressing  symptom  of  certain  diseases  of  the  dental  pulp;  while 
neuralgia,  generally  associated  with  morbid  affections  of  the  nerves 
which  are  distributed  to  the  teeth,  may  and  does  occur  in  connection 
with  any  sensory  nerve  of  any  part  of  the  body  remote  from  or  near 
to  the  head  and  neck. 

Definitions.- — The  two  words  odontalgia  and  neuralgia  may  thus  be 
defined :  odontalgia  is  pain  in  or  around  a  tooth  or  teeth ;  neuralgia 
is  pain  in  the  course  or  the  peripheral  distribution  of  a  sensory  nerve 
or  nerves. 

For  the  proper  comprehension  of  the  meaning  of  the  word  "pain" 
it  is  necessary  to  define  and  note  the  causes  and  laws  of  sensations. 


192  ODONTALGIA  AND  NEURALGIA 

"Pain"  can  shortly  be  translated  "a  disagreeable  sensation."  It  is 
not  easily  described,  but  for  present  purposes  this  definition  will 
suffice. 

Definition  of  Sensatio7i. — A  sensation  is  a  means  by  which  a  person 
is  made  aware  of  the  events  occurring  in  the  outside  world — the  means 
by  which  his  environment  acts  upon  him.  It  is  the  "consciousness 
of  an  impression  made  upon  the  mind  through  the  medium  of  a  nerve 
or  one  of  the  organs  of  sense."     (Starling.) 

Causes  of  Sensations. — Sensations  are  caused  by  some  movement  of 
molecules  or  masses  occurring  in  the  outside  world  which  act  upon  the 
sense  organs  and  convert  them  into  nerve  impulses  which  are  carried 
either  to  the  brain  or  spinal  cord.  In  the  case  of  the  former,  impulses 
give  rise  to  some  kind  of  so-called  reflex  action  which  may  be  either 
conscious  or  unconscious.  If  it  is  conscious,  the  person  becomes  aware 
of  a  sensation. 

The  five  senses — touch,  taste,  smell,  sight  and  hearing — do  not 
complete  the  number  of  different  sensations  experienced  by  the  human 
body.  There  are  really  eight,  all  told,  for  to  the  list  can  be  added  the 
sensations  of  temperature  changes  (heat,  cold  ^nd  their  variations), 
the  muscular  sense,  and,  finally,  pain. 

Laws  Governing  Sensations. — All  sensations  are  governed  by  two  laws: 
First,  the  law  of  specific  irritability,  which  states  that  every  sensory 
nerve  reacts  only  to  one  form  of  stimulus  and  gives  rise  to  one  form 
of  sensation.  In  other  words,  every  sensory  nerve  minds  its  own 
business.  The  second  law — the  law  of  proportionality — establishes 
the  fact:  "The  increase  of  stimulus  which  is  required  to  produce 
distinct  increase  of  sensation  always  bears  the  same  ratio  to  the  whole 
stimulus."  With  regard  to  the  muscular  sense  the  proportion  is  one 
in  forty,  in  the  tactile  or  pressure  sense  one  in  thirty. 

Pain  a  Distinct  Sense. — Pain  is,  as  has  already  been  observed,  an 
uneasy  or  disagreeable  sensation,  due  to  overexcitation  or  undue 
stimulation  of  a  sensory  nerve,  no  matter  what  the  nature  of  the 
stimulus.  Thus,  if  the  elbow  be  placed  in  a  dish  of  iced  water  the  trunk 
of  the  ulnar  nerve  is  stimulated,  and  pain  is  referred  to  the  third  and 
fourth  fingers  by  virtue  of  their  muscles  being  supplied  by  the  super- 
ficial palmar  branch  of  this  nerve.  If  the  so-called  "crazy-bone" 
sustains  a  blow  sensations  are  conducted  also  to  the  same  digits. 

Pain  is  a  distinct  sense.  It  is  not  an  exaggerated  tactile  or  tempera- 
ture sensation,  but  promoted  by  a  distinct  set  of  special  nerve  fibers, 
although  indistinguishable  under  the  microscope  from  motor,  sensory 
or  sympathetic  nerves.  It  is  a  well  known  clinical  fact  that  many 
patients  are  insensitive  to  pain,  yet  they  are  able  to  respond  immediately 
to  touch.  Many  patients  in  whom  the  tactile  sense  is  deficient  or 
absent,  suffer  from  an  exaltation  of  the  pain  sense.  Further,  certain 
areas  of  the  skin  afford  examples  of  the  existence  of  pain  "spots" 
which  are  similar  to  the  "heat  and  cold  spots"  found,  for  instance,  on 
the  palm  of  the  hand. 


ODONTALGIA  193 

In  certain  regions  of  the  body  only  one  sensation  is  experienced,  by 
whatever  means  induced.  The  cornea  is  capable  of  feeling  only  pain- 
ful sensations;  all  kinds  of  stimulation  are  converted  into  the  one 
sensation.  The  presence  of  foreign  substances  on  its  surface,  such  as 
a  piece  of  grit,  a  stray  eyelash,  a  chemical  irritant,  induces  pain. 

And  it  is  thus  with  the  teeth. 

In  normal  circumstances  teeth  do  not  feel  anything.  When  they 
are  occluded  in  the  ordinary  way  no  impression  is  recognized  by  the 
brain;  but  when  they  are  brought  into  contact  by  a  conscious  act,  the 
tactile  or  pressure  sense  is  established  and  the  brain  becomes  aware  of 
what  has  taken  place.  The  act  of  placing  a  finger  on  the  surface  of  a 
tooth  sets  up  weak  tactile  sensations,  and  the  brain  takes  cognizance 
of  the  fact  because  it  is  done  consciously.  The  same  argument  applies 
to  the  exercise  of  walking,  where,  ordinarily,  tactile  impressions  on  the 
soles  of  the  feet  are  not  felt  unless  the  act  is  being  accomplished 
consciously. 

It  is  therefore  obvious  that  as  the  dental  pulp  and  the  periodontal 
membrane  are  abundantly  supplied  with  sensory  nerves,  and  are  from 
this  viewpoint  special  sense  organs,  unable  to  differentiate  between 
the  several  kinds  of  stimulations,  these  two  tissues,  like  the  cornea, 
are  incapable  of  interpreting  the  various  kinds  of  stimulations  in  any 
other  term  than  the  one  of  pain.  Irritation  of  the  dental  tissues, 
whether  it  be  set  up  by  heat,  cold,  sweet,  sour,  bitter  or  acid  substances, 
electrical,  mechanical  or  bacteriological  disturbances,  is  translated  by 
the  dental  pulp  and  periodontal  membrane  into  pain. 

Anatomical  and  Physiological  Considerations. — ^The  exact  method  of 
conduction  of  impulses  from  outside  sources  to  the  pulp  is  still  a  matter 
of  controversy.  The  limits  of  this  article  do  not  allow  of  a  discussion 
of  the  subject;  but  it  may  be  stated  generally  that  the  enamel  of  the 
teeth,  being  merely  an  inorganic  substance — a  secretion  which  has 
undergone  calcification,  transmits  and  does  not  generate  sensations. 
It  conducts  any  of  the  above  mentioned  stimulations  to  the  dentine 
beneath.  The  latter  tissue,  probably  by  irritation  of  the  dentinal 
fibrils,  contained  in  its  manifold  canals,  in  its  turn  transmits  impulses 
to  the  pulp,  and  the  brain  responds  through  the  direct  paths  of  the 
nervous  mechanism  of  the  latter. 

The  reaction  time  in  man  differs  according  to  the  physical  condition 
of  the  subject  of  the  experiment,  the  length  of  the  so-called  "dilemma," 
and  other  circumstances,  but  may  be  considered  as  varying  from  0.15 
to  0.2  second.  Generally  speaking,  it  may  be  said  that  it  is  quicker 
than  an  ordinary  electrical  current. 

Varieties  of  Pain. — Pain  varies  in  character  and  type.  It  may  be 
(1)  direct  or  local;  (2)  indirect  or  reflex. 

1.  The  direct  form  occurs  after  a  local  injury,  e.  g.,  extraction  of  a 
tooth  at  the  place  in  the  mouth  where  removal  of  the  tooth  has  been 
effected. 

2.  The  indirect  form  occurs  at  a  distance  from  the  injury  or  disease, 

13 


194  ODONTALGIA  AND  NEURALGIA 

e.  g.,  some  functional  disturbances  or  pathological  conditions  of  the 
liver  set  up  pain  under  the  left  scapula,  others  in  the  epigastrium. 
Some  form  of  reflex  action  in  another  organ  or  organs  may  -be  referred 
to  the  teeth;  thus,  the  phenomenon  commonly  called  "setting  the 
teeth  on  edge"  may  be  produced  by  reflex  sensations  from  the  nerves 
of  hearing,  touch  or  sight.  A  friend  of  the  writer  once  told  him  that 
his  teeth  had  been  set  on  edge,  when  in  India,  by  observing  children 
in  certain  parts  of  the  country  sucking  sugar  cane.  Contact  with  the 
velvety  surface  of  the  skin  of  a  peach,  the  creaking  of  a  wheel,  may  also 
be  cited. 

Pain  varies  in  type.  It  may  be  sharp  or  dull,  agonizing,  lancinating, 
aching,  continuous,  intermittent,  localized  or  diffuse.  The  nature 
depends  on  the  cause  and  on  the  anatomical  peculiarities  of  the  tissue 
affected. 

In  making  the  diagnosis  of  the  cause  of  pain  great  attention  must 
be  paid  to  the  foregoing  types.  This  is  usually  an  easy  matter,  but 
at  times  extremely  difficult  on  account  of  complications. 

Causes  of  Odontalgia.^ — It  has  been  indicated  that  the  two  dental 
tissues  in  which  pain  may  originate  are  the  pulp  and  the  alveolo- 
dental  periosteum. 

Three  varieties  may  be  noted:  (a)  Local  odontalgia;  (6)  referred 
odontalgia,  and  (c)  obscure  odontalgia. 

(a)  Local  odontalgia  is  a  symptom  of  (1)  acute  or  chronic  hyperemia 
and  inflammation  of  the  pulp,  or  (2)  acute  or  chronic  hyperemia  and 
inflammation  of  the  periodontal  membrane;  (6)  referred  odontalgia 
is  a  symptom  of  any  condition  which  gives  rise  to  irritation  of  the 
peripheral  branches  of  the  fifth  pair  of  nerves  and  their  connections; 
(c)  obscure  odontalgia  occurs  in  teeth  without  any  obvious  visible 
lesion. 

Local  Odontalgia.^ — When  a  warm  solution  is  takenr  into  the  mouth 
and  induces  slight  odontalgia  it  indicates  that  the  vessels  of  the  pulp 
are  congested.  If  the  condition  remains  unrelieved  inflammation 
follows. 

Pain  in  acute  pulpitis  is  symptomatic  of  the  disease.  Its  intense 
character  is  due  to  the  fact  that  as  a  result  of  the  enlargement  of  the 
bloodvessels,  the  exudation  of  inflammatory  cells  and  products,  the 
inflammation  of  the  nerves  themselves,  and  the  increase  in  the  amount 
of  perivascular  material  taking  place  in  a  soft,  highly  vascular  tissue, 
incapable — owing  to  its  enclosure  in  dense,  unyielding  walls  of  dentine 
— of  expansion,  great  tension  is  brought  to  bear  on  the  already  inflamed 
sensory  nerves  distributed  throughout. 

The  phenomenon  is  somewhat  different  in  the  case  of  the  periodontal 
membrane.  It  is  here  modified  to  some  extent  by  the  swelling  of  the 
membrane  consequent  on  the  inflammatory  changes  going  on  within, 
being  compensated  by  a  slight  elevation  of  the  tooth  in  its  alveolar 
socket. 

In  the  early  stages  of  acute  periodontitis  pressure  on  the  offending 


ODONTALGIA 


195 


tooth  brings  immediate  relief;  for  blood  is  pressed  out  of  the  enlarged 
vessels,  which  thus  momentarily  return  to  their  normal  diameter  and 
capacity.  In  later  stages,  however,  the  walls  of  the  bloodvessels  do 
not  regain  their  elasticity,  nor  the  blood  current  its  equilibrium.  They 
remain,  therefore,  more  or  less  permanently  dilated;  hence  pressure 
increases  instead  of  diminishes  or  abolishes  pain. 

It  frequently  happens  that  both  pulp  and  periodontal  membrane 
are  affected.  The  types  of  pain  above  indicated  then  become  complex 
and  the  diagnosis  involved. 

The  following  differences  in  types  of  pain  in  uncomplicated  cases 
will  be  found  useful : 


Differential  Diagnosis  of  Acute  Inflammation  of: 


The  Dental  Pulp. 

1.  Pain:   Sharp,  shooting,  intermittent, 

throbbing,  reflected. 

2.  Temperature:      (a)    Cold  may  give 

rehef  in  early  stages;  (b)  heat  in- 
tensifies pain. 

3.  Inspection:    Tooth  normal  height. 

4.  Palpation:    Tooth  firm. 

5.  Percussion:   Negative. 

6.  Pressure:   Negative- 

7.  Cavity:   Generally  present. 

8.  Pain:  Increased  on  assuming  recum- 

bent position. 


The  Periodontal  Membrane. 

1.  Dull,   gnawing,   aching,   continuous, 

localized. 

2.  (a)   Cold  generally  gives  rehef;   (b) 

heat  does  not  alter  character  of 
pain. 

3.  Tooth  raised  in  socket  in  later  stages. 

4.  Tooth   loose  in  later  stages. 

5.  Induces  pain. 

6.  At  first  relieves  pain;  in  later  stages 

intensifies  it. 

7.  No  ca\aty. 

8.  Not  increased. 


In  view  of  the  fact  that  odontalgia  is  the  chief  sjniptom  of  acute  and 
chronic  pulpitis  and  periodontitis  and  their  complications,  the  causes 
of  these  conditions  are  identical  with  that  sjTiiptom.  They  may  be 
enumerated  as  follows: 

(A)  Acute  Pulpitis,  Including  Hyperemia. — (1)  The  toxins  of  caries- 
producing  organisms  of  dental  caries;  (2)  injury  to  the  dentine;  (3) 
extension  of  inflammation  from  the  periodontal  membrane;  (4)  cold; 
(5)  rheumatism  and  allied  constitutional  disorders;  (6)  abuse  of 
mercury,  taken  internally;  (7)  fillings,  inducing  thermal  conductions. 

(Bi)  Acute  Local  Periodontitis,  Including  Hyperemia. — I.  Septic 
conditions  set  up  by  (i)  extension  from  the  septic  pulp;  (ii)  dento- 
alveolar  abscess  arising  in  a  neighboring  tooth;  (iii)  "pyorrhea" 
pocket.  II.  Traumatic  disturbances  set  up  by  (i)  irritation  produced 
by  the  presence  of  tartar,  edge  of  badly-fitting  crown  or  denture;  (ii) 
malocclusion;  (iii)  improper  application  of  rubber  dam  clamp;  (iv) 
blow  on  a  tooth;  (v)  too  rapid  separation  of  teeth  before  filling  a  cavity; 
(vi)  too  rapid  movement  during  regulation;  (vii)  perforation  of  dentine 
of  root  through  the  side;  (viii)  passage  of  instruments  through  the  apex; 
and  (ix)  occasionally,  passage  of  root  filling  through  the  apex;  III. 
Chemical  causes  set  up  by  the  use  of  various  drugs. 

(B2)  Chronic  Local  Periodontitis  induced  by:  (i)  Septic  infection 
fropa  root  canal;  (ii)  Traumatism,  such  9,s  a  blow  on  a  tooth,  edge  of 


196  ODONTALGIA  AND  NEURALGIA 

tartar,  rough  edge  of  filling,  carious  cavity  at  gingival  margiti  retaining 
food  debris,  malocclusion,  imperfectly  contoured  filling,  and  delayed 
eruption  of  teeth. 

(B^)  General  Periodontitis  due  to  gout,  diabetes,  rheumatism,  syphi- 
litic stomatitis,  abuse  of  mercury,  insufficiency  of  mastication,  etc. 

Referred  Odontalgia.— The  commonest  form  of  referred  odontalgia 
is  expressed  in  the  pulp  of  a  tooth  which  is  not  in  itself  the  seat  of  the 
pain.  A  maxillary  molar  may  refer  its  pain  to  the  mandibular  molar 
on  the  same  side;  a  mandibular  third  molar  may  refer  its  pain  to  a 
mandibular  premolar.  Pressure  on  the  supra-orbital  branch  of  the 
frontal  division  of  the  ophthalmic  nei-ve  as  it  emerges  from  the  supra- 
orbital foramen  may  induce  odontalgia  in  the  maxillary  canine  of  the 
same  side.     The  pain  never  crosses  the  mid-line  of  the  face. 


Fig.  115. — Diagram  of  a  reflex  act.  The  sensory  nerves  in  (T)  the  tongue  and  (C) 
cheek  send  stimuH  to  (B)  the  brain,  which  transmits  them  to  (P)  the  dental  pulp.  Thus 
exceedingly  sweet  substances  on  the  tongue  will,  at  times  produce  odontalgia. 

Obscure  Odontalgia. — Odontalgia  may  occur  in  teeth  unaffected  by 
dental  caries.  It  is  then  due  to  one  of  the  following  causes:  (1) 
Increased  or  diminished  blood-pressure  in  the  pulp;  (2)  pulp  nodules; 
(3)  altered  chemical  constituents  of  the  blood;  (4)  intra-oral  electrical 
impulses;  (5)  reflex  from  tongue;  (6)  lesions  of  Vth  nerve;  (7)  general 
neurasthenia  and  debility. 

The  physiological  and  pathological  conditions  during  which  obscure 
odontalgia  may  arise  as  a  symptom  are  associated  with:  (1)  The  period 
of  puberty  in  boys  and  girls,  and  during  the  plethoric  habit  in  men, 
in  menstruation  or  menopause  in  women;  (2)  rheumatism  and  allied 
blood  diseases;  (3)  lack  or  deficiency  of  lime  salts  in  the  blood;  (4)  slight 
impulses  producing  weak  voltaic  currents  generated  during  operations 
about  the  mouth,  as  the  contact  of  dissimilar  metals  when  the  saliva 


NEURALGIA  197 

happens  to  be  sufficiently  ionized  (Fig.  110);  (5)  on  taking  very  sweet 
substances  into  the  mouth  under  certain  emotional  or  nervous  cir- 
cumstances (Fig.  115);  (6)  inflammation,  injury,  tumors,  and  (7) 
periods  of  mental  depression  following  overanxiety  or  overwork. 

In  all  of  these  there  is  no  visible  pathological  lesion  of  the  teeth, 
excepting  under  (4),  where  carious  cavities  have  been  filled  with  gold 
or  amalgam  and  occupy  a  large  area  of  the  tooth  surface. 


Fig.  116. — Diagram  of  a  reflex  act.  An  electrical  impulse  may  set  up  momentary 
odontalgia  when  two  dissimilar  metals,  such  as  those  of  the  edge  of  a  hand  mirror  (M) 
and  (F)  of  metallic  filling,  meet,  and  the  circuit  is  completed  by  (C)  the  mucous  mem- 
brane of  the  cheek,  the  saliva  acting  as  the  electrolyte. 

NEURALGIA. 

Definition. — Neuralgia  is  pain  in  the  course  of  a  sensory  nerve,  or 
within  its  area  of  distribution. 

Neuralgia  is  an  extremely  general  symptom  of  some  of  the  phases 
of  many  nervous  disturbances  occurring  in  any  part  of  the  body. 
Commonest  when  affecting  the  head  and  neck,  and  associated  chiefly 
with  the  trigeminal  nerve,  this  symptom  of  disease  may  become  the 
most  terrible  affliction  to  which  man  is  subject.  It  may  be  regarded 
as  a  serious  sign,  for  the  accumulated  results  of  long-continued  pain 
may  lead  to  severe  mental  and  constitutional  conditions  which  are  very 
difficult  to  treat  successfully. 

Nature  and  Type. — ^The  character  of  the  pain  varies  considerably. 
It  is,  however,  well  differentiated  from  odontalgia.  Thus,  it  may 
be  sudden  .and  violent  with  decided  remissions  and  intermissions;  it 
may  be  recurrent,  alternating  and  periodic;  it  may  be  shooting,  piercing 
and  penetrating.  It  generally  commences  quite  suddenly,  spasmodi- 
cally, and  without  warning,  and  increases  gradually  to  a  climax  of 
intense  exacerbation,  th^en  slowly  or  rapidly  subsides.  The  attacks 
may  last  for  minutes,  or  hours,  or  days.  The  writer  recalls  a  case 
where  the  most  agonizing  pain  lasted  for  fifteen  minutes  at  a  time,  then 
passed  away  for  a  short  period,  only  to  return  again  with  increased 
vehemence.  Slight  exciting  causes  may  induce  neuralgia,  such  as  a 
sudden  noise,  like  the  banging  of  a  door,  a  draft  of  air.  Pressure  on 
the  trunk  of  the  affected  nerve  may  occasion,  or  relieve,  or  intensify 


198  ODONTALGIA  AND  NEURALGIA 

the  pain.  The  parts  in  the  neighborhood  of  the  nerve  may  become 
affected;  muscles  may  become  spasmodically  contracted;  the  skin 
hyperemic  and  swollen,  and  the  secretions  from  the  sweat-glands 
excessive  in  amount.  Skin  eruptions,  such  as  herpes  of  the  lip  may 
occur,  and  the  temporomandibular  joint  become  tender,  and  a  kind 
of  trismus  produced. 

Causes. — The  general  and  local  constitutional  disorders  of  which 
neuralgia  is  a  s^Tuptom  may  be  difficult  to  determine.  Among  them 
hysteria,  mental  depression,  migraine,  neurasthenia,  general  debility, 
malaria,  anemia,  inffuenza,  difficult  dentition  and  unerupted  teeth  in 
children,  may  be  suspected;  while  tumors  of  the  brain,  injuries  to  nerve 
trunks,  various  forms  of  neuritis,  and  tumors  of  the  nerves  may  also  be 
enumerated. 

Edentulous  persons,  in  whom  much  atrophy  of  the  alveolar  processes 
of  the  jaws  has  occurred  as  a  result  of  premature  loss  of  the  teeth, 
frequently  experience  neuralgia  through  pressure  set  up  by  wearing  a 
denture.  In  this  way  the  mandibular  nerve,  though  unexposed  in  the 
mandibular  canal,  is  often  affected. 

Varieties.  ^ Four  true  types  of  neuralgia  have  been  described: 
(1)  Neuralgia  Qiiinti  Major — the  tic  douloureux  of  some  authors;  (2) 
Neuralgia  Quinti  Minor;  (3)  neuralgia  secondary  to  disease  of,  or  injury 
to,  or  pressure  upon  a  cranial  nerve,  as  a  tumor  of  the  trunk  of  the 
trigeminal,  and  (4)  neuralgia  secondary  to  general  disease  such  as 
anemia,  etc. 

Neuralgia  Quinti  Major  may  begin  either  in  the  Gasserian  ganglion 
or  in  the  peripheral  distribution  arising,  as  Sir  Victor  Horsley  first 
described,  from  an  ascending  neuritis  due  to  chronic  osteitis  of  the 
sockets  of  the  teeth. 

Neuralgia  Quinti  Minor  is  a  visceral  referred  pain  due  to  chronic 
pulpitis,  chronic  periodontitis  and  their  complications.  It  may  be 
explained  thus:  "When  impulses  pass  up  sensory  nerves  from  a 
tooth  which  is  diseased,  they  set  up  a  disturbance  in  that  segment  of 
the  nervous  system  to  which  they  are  conducted.  Any  second  sensory 
impulse  from  another  part,  e.  g.,  from  the  surface  of  the  face,  which 
happens  to  pass  into  that  segment  will  be  profoundly  altered  in  charac- 
ter, for  it  no  longer  falls  into  a  normal  but  into  an  actively  disturbed 
segment  of  the  nervous  system.  The  resulting  stimulus  therefore 
becomes  more  exaggerated  in  character." 

On  the  face  these  areas  represent  the  segmental  origin  of  the  nerves 
that  give  rise  to  heat,  cold  and  pain. 

This  part  of  the  subject  has  been  thoroughly  investigated  by  Valleix 
and  Prof.  Henry  Head,  who  has  mapped  out  on  the  skin  certain  well- 
defined  regions  which  are  under  the  influence  of  the  individual  teeth. 

The  accompanying  illustrations  (Figs.  117  to  124)  demonstrate 
graphically  these  areas,  and  need  not  be  fully  described.  The  reader 
is  referred  to  the  writer's  "Dental  Anatomy  and  Physiology,"  or 
the  original  article  in  Brain,  Part  III,  1894. 


NEURALGIA 


199 


Bordering  upon  the  line  between  physiological  and  pathological 
pain,  if  one  may  use  such  a  term,  is  an  unusual  ali'ection  or  disturbance, 


f 


Fig.  117. — The  frontonasal  area  (maxil- 
lary incisors) .  In  this  and  the  succeeding 
figures,  the  "maximum  spots"  of  intensity 
of  pain  are  indicated  by  a  round  white  dot. 


Fig.  118. — The  nasolabial  area.     (Maxil- 
lary canine  and  first  premolar.) 


¥ 


Fig.  119. — The  temporal  area, 
gecond  premolar.) 


(Maxillary 


i 

Fig.  120. — The  maxillary  area. 
(Maxillary  second  premolar  or  first 
molar) . 


not  a  disease,  of  the  trigeminal  nerve,  similar  perhaps  in  origin  to  a 
hemicrania  when  due  to  hyperemia  of  the  vessels  of  the  cerebrum. 


200 


ODONTALGIA  AND  NEURALGIA 


Hughlings  Jackson  says  one  form  is  due  to  digestive  derangements. 
Here  changes  in  the  feeding  customs  of  an  individual — digestive  changes 
or  altered  constructive  metabolism  due  to  a  newly  acquired  fasting  or 


Fig.  121. — The   mandibular    area.     (Maxillary 
second  and  third  molars.) 


Fig.  122.  —  The  mental  area. 
(Mandibular  incisors,  canine  and 
first  premolar.) 


Fig.  123. — The  hyoid  area.  (Mandibular 
second  premolar,  and  first  and  second 
molars.) 


Fig.  124. — The  superior  laryngeal  area. 
(Mandibular  third  molar.) 


NEURALGIA  201 

semi-fasting  habit — may  and  do  often  set  up  odontalgia  and  neuralgia, 
very  diflficult  of  diagnosis  by  dentist  and  physician.  Located  and 
limited  to  one  side  of  the  face,  it  is  always  the  same  side  or  alternate, 
sides  of  the  face  which  are  afi'ected,  as  if  one  of  the  pairs  of  the  Vth 
nerve  was  more  susceptible  for  some  reason  to  these  changes,  and  as  if 
the  brain  was  content  in  indicating  the  presence  of  a  deep-seated 
disturbance  only  by  one,  and  not  by  two  routes.  It  spreads  over  a 
large  area  and  does  not  involve  the  mastoid  region  or  concha  of  the 
ear.  It  is  increased  on  deep  pressure  outside  of  the  jaw,  over  the  root 
of  the  tongue. 

The  pain  is  heavy,  dull,  sporitaneous,  persistent,  deeply  planted, 
apparently  in  the  body  of  the  mandible,  maxilla  or  cheek.  The  soft 
palate,  tongue  and  tonsils  are  unaffected.  It  may  last  for  a  haK  hour 
or  less  and  then  disappear.  No  maximum  spots  of  intensity  are 
noticed.  Digital  pressure  increases  it;  hot  and  cold  objects  have  no 
effect,  though  cold  may  at  times  relieve  it.  Pressure  as  from  a  soft 
substance,  like  a  cushion  or  pillow,  produces  an  exacerbation. 

The  teeth  are  very  sensitive.  A  cold  finger  gently  passed  over  their 
crowns  increases  the  pain;  pressure  and  percussion  do  not.  Occlusion 
of  the  opposing  teeth  does  not. 

Excluding  migraine,  the  cause  of  the  trouble  appears  to  be  anemia 
or  metabolic  disturbances  of  the  sjTiipathetic  nervous  system,  due  to 
slight  temporary  gastric  disturbance  set  up  by  malnutrition  or  influenza. 

A  full,  easily  digested  meal  will  usually  relieve  the  pain,  while  the 
exhibition  of  drugs,  such  as  acetophenetidin,  in  5-grain  doses,  is  also 
indicated.  Tonics  and  general  attention  to  health  should  also  be 
advised. 

Treatment. — ^Little  need  be  here  said  about  the  therapeutic  measures 
which  are  available  for  the  relief  of  odontalgia  and  neuralgia,  for  it  is 
obvious  that  the  treatment  of  the  symptom  and  not  the  cause  of  the 
symptom  is  unscientific  and  incorrect.  Odontalgia  can  be,  and  is, 
treated  with  much  success  by  a  skilful  dentist,  but  neuralgic  conditions 
should  be  treated  by  common  sense  cooperation  with  the  physician 
and  surgeon.  It  is  therefore  the  duty  of  the  dentist  to  call  in  a  medical 
man  in  consultation  in  cases  needing  his  help  for  the  relief,  if  not  the 
cure  of  the  disorders  which  have  led  to  the  production  of  the  above 
distressing  symptoms. 

Conclusion. — It  may  be  stated  in  general  terms  that  if  reasonably 
hot  and  cold  foods  and  drinks  can  be  taken  into  the  mouth  without 
inducing  odontalgia  or  neuralgia  the  dental  pulps  of  the  teeth  are 
in  good  condition;  and  that  if  no  obvious  cause  for  odontalgia  is  present, 
such  as  a  carious  cavity,  such  symptoms  must  be  looked  for  elsewhere. 
Hyperemia  of  the  pulp  is  indicated  and  may  be  diagnosed  if  pain  is 
experienced  at  a  localized  situation  on  holding  warm  fluids  in  the 
mouth,  especially  if  a  breach  of  enamel  or  dentine  is  associated  with  it. 

If  this  examination  fails  and  the  pain  still  persists,  the  tongue  may 
next  be  suspected  and  thoroughly  inspected  and  tested  for  nerve 


202  ODONfALGlA  AND  NEURALGIA 

reflexes;  then  general  constitutional  causes — vascular  disturbances 
due  to  puberty,  menstruation,  pregnancy,  the  climacteric,  etc., 
conjectured,  and  finally,  degenerative  conditions  of  the  dental  pulp 
may  be  diagnosed. 

The  prompt  recognition  of  these  latter  changes  will  be  convincing 
alike  to  patient  and  dentist,  and  the  solution  of  some  of  the  problems 
of  odontalgia  and  neuralgia  satisfactorily  determined. 


CHAPTER  X. 

THE  RELATION  OF  ORAL  INFECTIONS  TO  GENERAL 
HEALTH. 

By  KURT  H.  THOMA,  D.M.D. 

Infection  in  the  jaws  is  not  a  modern  disease.  Centuries  ago  tooth 
abscesses  were  common  among  the  Egyptians  of  the  predynastic 
period,  as  well  as  of  the  Old  and  Middle  Empires.  In  a  study  which 
the  writer  made  at  the  Peabody  Museum  of  a  large  number  of  Egyptian 
crania  it  was  found  that  as  far  back  as  4800  B.C.  people  suffered  from 
alveolar  abscesses.  This  was  evident  from  the  bone  destruction  seen 
around  diseased  teeth.  The  condition,  however,  arose  then  from  a 
source  different  from  its  origin  today.  Instead  of  decay  leading  to  the 
pulp  infection,  the  primary  cause  was  abrasion  of  the  tooth  surface, 


Fig.  125 


that  is,  wearing  away  of  the  tooth  until  the  pulp  became  exposed 
(Fig.  125,  A).  This  abnormal  wear  on  the  teeth  was  caused  by  the 
coarseness  of  the  food,  as  well  as  by  the  grit  present  in  their  cornmeal 
after  its  preparation  in  stone  mortars.  The  infection,  which  gained 
entrance  in  this  way,  proceeded  through  the  opening  in  the  root  into 
the  surrounding  bone,  as  it  does  today  (Fig.  126).  In  those  days, 
however,  the  opening  in  the  tooth  was  not  sealed  up  by  a  root  canal 
filling  and  so  there  was  a  permanent  outlet  for  accumulating  pus. 

In  our  time  oral  infections  are  so  common  that  there  are  very  few 
people  who  have  not  at  least  one  abscessed  tooth.  On  account  of  the 
chronic  character  of  most  of  these  infections,  patients  as  a  rule  are 
entirely  unaware  of  their  existence.    The  frequency  of  such  lesions  is 


204 


RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 


well  brought  out  by  Dr.  Black  of  Chicago,  in  statistics  which  he  com- 
piled from  roentgen  pictures  of  all  the  teeth  of  300  people.  These 
examinations  were  not  made  because  of  any  complaint,  or  indication  of 
treatment  and,  therefore,  they  represent  as  near  an  average  of  such 


Fig.  126 


conditions  as  can  be  obtained.     The  following  tabulation  gives  the 
result: 


Number  of  patients 

Age. 

Percentage  of 

examined. 

Years. 

dental  affections 

86 

.      .      .      .     Under  25 

56 

53 

.      .      .      .                  25  to  29 

72 

68      .      .      . 

.      .      .      .                 30  to  39 

87 

53 

.      .      .      .                  40  to  49 

89 

40 

.■     .      .      .        Over  50 

100 

PERIAPICAL  INFECTIONS. 

The  most  important  oral  infections  to  be  considered  in  connection 
with  the  general  health  are  those  affecting  the  periapical  tissues. 
The  infection  nearly  always  enters  through  the  root  canal,  but  occa- 
sionally it  finds  its  way  to  the  inside  of  the  jaws  through  a  pus  pocket 
along  the  side  of  the  root  of  a  tooth.  Infection  from  the  root  canal 
may  result  either  from  an  acute  or  chronic  pulpitis  caused  by  decay, 
from  a  necrotic  pulp  or  an  infected  root  canal  which  has  not  been 
properly  sterilized  and  filled,  or  from  root  canal  instrumentation. 
Fig.  127  shows  a  photomicrograph  of  a  molar  with  a  cavity  from  which 
bacteria  penetrated  into  the  pulp  through  the  dentinal  canals,  forming 
a  large  abscess  (A)  in  the  pulp  chamber.  The  nerves  of  the  pulp  have 
been  pressed  to  one  side  and  surround  the  abscess.  Fig.  128  shows 
a  roentgen  picture  of  a  tooth  where  the  infection  has  started  from  a 


PERIAPICAL  INFECTIONS 


205 


pocket  (A)  on  the  mesial  side  of  a  molar.  When  the  apex  of  the 
tooth  was  reached  an  abscess  formed,  which  infected  the  pulp  in  this 
otherwise  healthy  tooth. 


Fig.  127 


W^ ' 


Fig.  128 


Periapical  infection  may  follow  either  of  two  distinct  chains  of 
pathological  changes.  The  first  is  of  a  destructive  nature  and  begins 
with  a  reaction  causing  all  the  symptoms  of  acute  inflammation,  while 


206  RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 

the  other  from  the  beginning  is  characterized  by  a  mild  and  chronic 
reaction,  which  starts  and  continues  without  giving  any  local  symptoms. 

Acute  Periapical  Infection. — This  condition  starts  as  acute  peri- 
odontitis and  involves  a  violent  inflammatory  reaction  of  the  tissue. 
Purulent  exudations  soon  accumulate,  the  cells  of  the  peridental  mem- 
brane and  the  surrounding  bone  become  destroyed  and  the  condition 
is  then  called  an  acute  alveolar  abscess.  This  may  spread  and  cause 
suppurating  ostitis  of  greater  extent,  or  the  pus  may  soon  find  an  outlet 
to  the  surface  via  the  Haversian  canals,  which  penetrate  the  outer 
cortical  layer  of  bone.  When  the  pus  collects  under  the  periosteum,  a 
reaction  sets  in  at  once,  causing  a  widespread  serous  infiltration  of 
the  soft  parts,  the  cheek  or  neck.  Finally  the  pus  burrows  a  channel 
through  the  soft  tissue,  forming  a  fistula  into  the  mouth,  nose,  maxillary 
sinus,  or  outside  of  the  face.  After  this  process  of  destruction  has 
reached  its  climax  Nature  makes  an  attempt  at  repair  and  the  acute 
symptoms  disappear,  but  unless  the  cause  (a  diseased  pulp  or  necrosed 
root  apex)  is  removed  the  condition  becomes  chronic.  In  this  stage  it 
may  last  for  an  indefinite  period  with  the  fistula  discharging  pus  if  the 
destructive  process  becomes  more  active,  or  closing  up  for  a  time  if  the 
defensive  system  predominates,  only  to  reopen  with  more  or  less  marked 
subacute  symptoms  when  suppuration  again  becomes  more  active. 

Blind  Abscess  or  Dental  Granuloma. — The  difference  between  an 
acute  alveolar  abscess  and  a  blind  abscess,  or  dental  granuloma,  should 
be  clearly  understood.  The  former  is  a  suppurative  inflammation  and 
involves  a  process  of  destruction  of  the  peridental  tissues,  dissolving 
them  into  pus.  The  latter  is  a  reaction  to  a  mild  infection,  stimulating 
inflammatory  new  growth  and  active  suppuration  does  not  occur  at 
first,  but  an  exacerbation  may  change  the  pathological  picture  later 
so  as  to  simulate  a  typical  acute  alveolar  abscess.  The  blind  abscess, 
or  granuloma,  begins  and  continues  to  grow  without  giving  any  symp- 
toms. The  defensive  system  of  the  body  takes  care  of  the  slight 
amount  of  pus  formed,  which  is  absorbed  through  the  lymphatics,  or 
blood  channels.  Sometimes  a  dental  granuloma  is  described  as  being 
a  tumor,  but  this  is  not  correct,  as  it  is  distinctly  of  infectious  origin 
and  histologically  presents  a  picture  of  chronic  inflammation.  The 
lesion  of  course  increases  at  the  expense  of  the  bone.  A  picture  of  a 
skull  (Fig.  129)  showing  such  a  tooth  will  illustrate  the  condition.  It 
shows  a  bicuspid,  the  root  canal  of  which  has  probably  been  treated. 
The  hole  in  the  bone  (A),  with  the  many  fine  canals  surrounding  it, 
represents  the  amount  of  destruction  which  has  taken  place.  Another 
picture  (Fig.  130)  shows  a  tooth  with  a  chronic  abscess,  as  seen  under 
the  microscope.  This  abscess  is  what  fills  the  hole  in  the  bone.  It 
shows  the  end  of  a  root  (A),  to  which  is  attached  a  small  sac  (B). 
This'has  been  stained  with  a  connective  tissue  stain,  so  as  to  bring  out 
the  fibrous  nature  of  the  capsule  (C)  surrounding  the  lesion.  The 
inner  part  shows  three  centers  of  broken  down  tissue  and  if  examined 
with  a  high  power  lens  it  would  be  found  to  contain  many  vessel^ 


PERIAPICAL  INFECTIONS 


207 


surrounded  by  large  numbers  of  lymphocytes,  plasma  cells  and  leuko- 
cytes.    These  have  special  biological  functions.     The  first  two  are 


Fig.  129 


Fxq.  130 


208 


RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 


said  to  neutralize  and  eliminate  toxins,  while  the  latter  are  of  phago- 
cytic nature,  destroying  and  fighting  the  invading  bacteria.  Pus  is 
continually  formed  in  small  quantities  in  the  abscess.  There  is 
generally  no  outlet,  the  original  opening  through  the  root  canal  and 
cavity  in  the  crown  having  been  closed  by  the  filling,  so  that  the  pus 
is  taken  up  by  the  blood  stream  and  carried  away. 

Condition  of  the  Tooth  Apex. — Periapical  infection,  especially  if  it  is  of 
long  standing,  causes  changes  in  the  cementum  of  the  tooth.  Nutri- 
tion is  usually  disturbed,  the  cells  of  the  apical  part  of  the  peridental 
membrane  may  become  destroyed  and  the  cementum,  which  is  very 


Fig.  131 


porous  and  easily  absorbs  the  products  of  inflammation,  becomes  pus- 
soaked  and  filled  with  bacteria.  In  this  condition  the  tooth  is  an 
obnoxious  foreign  body  which  Nature  tries  to  eliminate  by  osteoclastic 
absorption,  starting  on  the  surface  of  the  cement,  which  then  presents 
a  roughened  appearance  (Fig.  131,  A).  Marked  indentations  are  formed 
and  the  cement,  and  later  the  dentine  also,  dissolves.  At  times  new 
cement  is  deposited,  due  to  stimulation  of  cementoblasts,  which  have 
survived.  This  causes  enlargements  of  the  root  end  and  often  renders 
extraction  of  the  tooth  extremely  difficult.  The  reason  why  an  abscess 
of  long  standing  is  so  stubborn  and  impossible  to  eliminate  by  any 
means  other  than  surgical  treatment  is  on  account  of  the  infection  of  the 


EXTENSIVE  LESIONS  CAUSED  BY  PERIAPICAL  INFECTION     209 

apical  part  of  the  tooth  root,  which  is  a  dead  piece  of  bone  and,  like  a 
sequestrum,  has  to  be  removed  before  healing  can  take  place.  The 
process  of  absorption  indicates  plainly  that  Nature  wants  to  accom- 
plish the  elimination  of  the  tooth.  Fig.  132  illustrates  a  photomicro- 
graph of  a  tooth  with  a  blind  abscess  (A),  showing  absorption  (B), 
not  only  of  the  outer  layer  of  cement,  but  the  entire  apex  of  the  root. 


Fig.  132 

Exacerbations. — If  more  pus  is  formed  than  can  be  taken  care  of 
and  eliminated  by  means  of  absorption  it  may  result  in  the  formation 
of  a  fistula.  This  is  generally  known  as  a  gum-boil.  Everyone  knows 
that  a  great  deal  of  pus  can  be  squeezed  from  a  gum-boil  several  times 
a  day  and  this  makes  it  easier  to  understand  that  such  pus,  when 
drained  into  the  system,  must  be  injurious  to  the  health. 


MORE  EXTENSIVE  LESIONS  CAUSED  BY  PERIAPICAL  INFECTION. 

If  we  consider  the  frequency  of  dental  infections  it  is  surprising  how 
rarely  we  find  extensive  bone  infection  and  serious  involvement  of  the 
adjoining  structures  and  the  alveolar  process.  The  reason  for  this  is 
probably  to  be  found  in  the  bountiful  blood  supply  of  the  bone  in  the 
immediate  neighborhood  of  the  roots  of  each  tooth,  from  which  a 
defensive  system  is  built  up  to  prevent  the  spreading  of  infection,  carry- 
14 


210 


RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 


ing  away  the  products  of  bacterial  activity  so  successfully  that  there 
is  seldom  even  an  outlet,  or  fistula,  formed  to  the  face  or  gum.  Peri- 
dental infections  sometimes  result  in  extensive  lesions  of  the  jaw,  as 
well  as  radicular  or  periodontal  cysts,  which  are  also  of  the  infectious 
type.  It  is  a  deplorable  fact  that  they  are  generally  not  recognized 
for  a  long  time  and  are  often  treated  for  months  by  means  of  root  canal 
medication  without  making  an  accurate  diagnosis. 


Fig.  133 


Fig.  134 


Ostitis. — This  is  a  bone  infection  of  a  more  extensive  type,  developing 
often  from  periapical  infections.  It  may  be  of  the  suppurative  type, 
accompanied  by  violent  acute  symptoms,  but  more  often  is  of  chronic 
character,  developing  from  chronic  periapical  infection.  This  type  is 
called  granulating  ostitis.     It  may  involve  large  portions  of  the  jaw 


EXTENSIVE  LESIONS  CAUSED  BY  PERIAPICAL  INFECTION     211 

and  several  teeth  without  causing  much  swelHng  or  pain.  A  roentgen 
picture  of  granulating  ostitis  is  shown  in  Fig.  134.  Note  the  large, 
dark  area  of  irregular  outline,  marked  A.  Fig.  133  shows  a  picture  of 
an  ordinary  blind  abscess  (A)  for  comparison. 

Diffuse  Osteomyelitis. — This  condition  is,  fortunately,  very  rare, 
but  when  it  occurs  is  a  serious  disease.  It  spreads,  as  a  rule,  from  one 
side  of  the  jaw  to  the  other  and  with  the  best  of  care  it  often  takes 
months  for  complete  recovery.  Fig.  135  shows  such  an  infection, 
which  started  from  an  abscessed  tooth,  improperly  treated.  When 
the  dentist  finally  extracted  it  the  disease  had  already  spread  all  over 
the  jaw,  as  indicated  in  the  roentgen  picture  by  the  dark  channels 
extending  throughout  the  jaw. 


Fig.  135 

Cysts. — Cysts  are  found  quite  frequently.  The  writer  has  seen  a 
large  number  during  the  last  few  years.  They  are  caused  by  chronic 
abscesses  and  as  their  secretions  accumulate  they  increase  to  enormous 
size.  They  form  a  large  cavity  in  the  bone,  which  sometimes  reaches 
the  size  of  a  hen's  egg  and  always  contains  pus.  The  bone  itself  is  not 
infected,  but  is  absorbed  and  becomes  so  thin  sometimes  that  it  can  be 
bent  when  pressed  with  the  finger.  In  the  upper  jaw  cysts  may  en- 
croach on  the  nasal  cavity  or  develop  inside  the  maxillary  sinus,  some- 
times filling  it  almost  completely,  a  condition  which  is  very  difficult 
to  diagnose.  In  the  lower  jaw  they  are  found  in  the  body  of  the  man- 
dible, as  well  as  in  the  ramus.  Radicular  cysts  sometimes  have  appar- 
ently no  connection  with  a  tooth  root.  In  such  cases  the  guilty  tooth 
may  have  been  extracted,  the  cyst  having  escaped  notice  at  the  time, 
or  there  may  have  been  left  in  the  jaw  an  epitheliated  granuloma,  which 
developed  into  a  cyst  later.  Fig.  136  shows  such  a  case.  A  indicates 
the  cyst. 

The  diagnosis  of  a  cyst  is  easily  made  by  means  of  roentgen  pictures. 


212 


RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 


The  examination  should  be  made  on  large  films  or  plates,  as  the  small 
ones  seldom  cover  more  than  a  part  of  the  lesion.    The  cyst  cavity 


Fig.  136 


appears  as  a  black  area  on  the  negative  because  it  decreases  the  resist- 
ance which,  in  normal  bone  conditions,  is  put  in  the  way  of  the  rays. 


Fig.  137 


The  bone  immediately  surrounding  the  cavity,  however,  is  usually 
cortical  and  dense  and  so  we  find  the  typical  picture  of  a  cyst  showing 
a  light,  but  distinct,  surrounding  line  {A),we\\  illustrated  in  Fig.  137. 


INFECTED  TEETH  AS  A  SOURCE  OF  SYSTEMIC  DISEASE     213 

Infection  of  the  Maxillary  Sinuses. — Maxillary  sinusitis  in  both  the 
acute  and  chronic  types  is,  in  a  large  percentafi;e  of  cases,  due  to  dental 
infections.  Abscesses  on  the  upper  bicuspids  and  molars  are  frequently 
the  cause  of  infection  of  the  maxillary  antra.  Fig.  138  shows  the 
intimate  relation  of  the  tooth  apices  with  the  antrum  {A).  Only  a 
very  thin  layer  of  bone  separates  the  tooth  from  the  mucous  membrane 
of  the  sinus.  Acute  sinus  infection  may  be  caused  by  careless  instru- 
mentation or  the  pushing  of  an  infected  root  into  the  antrum.  Chronic 
maxillary  sinusitis  with  polypoid  degeneration  is  a  condition  which 
also  often  occurs  without  the  patient's  knowledge  and  may  be  dis- 
covered only  during  a  routine  examination.  If  abscessed  teeth  are 
found  in  the  upper  jaw  the  sinuses  should  always  be  investigated,  and 
in  all  cases  of  maxillary  sinus  disease  the  examining  physician  should 
insist  upon  roentgen  films  of  the  teeth. 


Fig.  138 

Ludwig's  Angina. — Ludwig's  angina  is  also  one  of  the  consequences 
of  alveolar  abscesses.  Most  cases  observed  by  the  waiter  have  followed 
the  extraction  of  teeth,  the  infection  spreading  rapidly  and  causing  an 
acute  infiltration  of  the  soft  tissues  of  the  floor  of  the  mouth.  The 
board-like  swelling  presses  the  tongue  upward  and  backward  into  the 
pharynx,  which  causes  the  well-known  symptoms,  difficulty  in  breath- 
ing and  swallowing  and  great  anxiety  on  the  part  of  the  patient.  The 
mortality  from  this  infection  is  very  great.  Death  may  occur  in  from 
ten  to  twenty  days. 

INFECTED  TEETH  AS  A  SOURCE  OF  SYSTEMIC  DISEASE. 

Since  the  days  of  Hippocrates  it  has  been  known  that  infections  of 
dental  origin  may  be  accompanied  by  serious  systemic  symptoms. 
This  celebrated  writer,  who  was  born  four  hundred  and  sixty  years 
before  Christ,  makes  the  following  statement:  "At  the  approach  of 
dentition  pruritis  of  the  gums  occurs  and  fevers,  convulsions  and 


214  RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 

diarrhea,  especially  when  cutting  the  canine  teeth."  The  eruption  of 
the  teeth,  therefore,  must  have  been  frequently  attended  by  acute 
infection.  This  is  the  first  writer  who  mentioned  the  effects  of  dental 
infections  upon  the  general  system. 

In  any  infection  we  have  both  local  and  general  effects.  The 
general  effects  in  acute  infections  come  on  suddenly  and  are  well 
marked,  even  alarming.  This  is  principally  due  to  the  fact  that  the 
cause  is  a  strong  injurious  agent,  such  as  very  pyogenic  organisms.  In 
chronic  inflammation  we  have  a  reaction  to  a  mild  injurious  agent  and 
the  systemic  effects  come  on  slowly  and  may  even  be  so  slight  that  no 
symptoms  occur  as  long  as  the  protective  forces  of  the  body  are  able  to 
take  care  of  the  condition.  However,  as  soon  as  the  general  resistance 
of  the  body  is  lowered  by  such  things  as  debilitating  disease,  poor 
physical  condition  or  pregnancy,  or  if  the  local  resistance  of  a  part  is 
decreased  by  exposure  or  interference  with  nutrition,  serious  complica- 
tions may  gradually  develop  and  frequently  the  patient  is  not  aware  of 
the  trouble  until  irreparable  harm  is  done.  The  following  observation 
of  two  patients  may  serve  as  an  illustration.  The  first,  a  woman  with 
a  perfectly  healthy  heart.  Hospital  Case  No.  225,  and  the  other,  a 
patient  with  a  weak  heart.  Hospital  Case  No.  211,  both  had  the  same 
amount  of  vaccine  injected.  The  first  patient,  a  well  developed  and 
well  nourished  woman,  had  been  suffering  from  chronic  arthritis  for 
twenty-one  months.  Lungs,  normal;  heart  sounds  regular  and  of 
good  quality.  On  February  20  vaccine  treatment  was  begun.  Injec- 
tion of  75,000,000  typhoid  bacteria  with  100  c.c.  of  normal  salt  solution 
was  made  at  3.30  p.m.  into  the  median  basilic  vein.  She  had  a  definite 
chill,  which  lasted  twenty  minutes,  but  otherwise  there  were  no  heart 
symptoms.  Temperature  and  pulse  curve  shown  on  chart  (Fig.  139). 
By  9.30  these  were  perfectly  normal.  A  second  vaccine  treatment  of 
100,000,000  bacteria,  given  eight  days  later,  produced  a  similar  result. 

The  second  patient,  a  woman  36  years  old,  was  admitted  for  chronic 
arthritis.  Had  had  measles,  diptheria  and  scarlet  fever  when  a  child; 
at  the  age  of  twelve,  "St.  Vitus'  dance,"  which  lasted  two  years;  two 
attacks  of  pneumonia  when  fifteen  years  old  and  rheumatic  fever  seven 
years  ago.  Her  present  illness  began  eighteen  months  ago,  when  she 
noticed  pain  and  stiffness  in  the  knees.  The  joints  of  the  fingers, 
elbows  and  shoulders  then  became  involved.  Present  examination 
shows  slight  edema  in  ankles,  teeth  poor,  glandular  enlargement  in 
submaxillary  region  on  both  sides.  There  was  a  systolic  murmur  of 
the  heart,  but  no  evidence  of  physiologic  disease.  On  February  15 
at  4.15  P.M.  the  patient  received  a  vaccine  injection  of  75,000,000 
bacteria  intravenously.  At  5  p.m.  there  were  signs  of  reaction,  chill, 
typical  spasmodic  shaking,  but  no  complaint  of  cold.  Had  marked 
cardiac  symptoms  at  9  p.m.  Patient  was  dyspneic,  cyanotic  and  cough- 
ing. Sputum  was  salmon  colored.  Distress,  dyspnea  and  headache 
lasted  until  about  midnight  and  the  next  day  there  was  still  tender- 
ness and  palpitation  over  the  precordia  (Fig.  139,  B), 


INFECTED  TEETH  AH  A  SOURCE  OP'  SYSTEMIC  DISEASE    ^15 

These  two  cases  illustrate  the  different  effect  on  two  patients  of  a 
small  and  limited  amount  of  toxin,  the  same  in  both  cases.  The  healthy 
patient,  in  this  case  the  one  with  the  strong  heart,  can  easily  take  care 
of  a  slight  infection,  while  another  patient  not  in  perfect  health  may 
suffer  from  a  similar  cause  most  severe  effects. 


Fig.  139 


Systemic  EfEects  from  Acute  Dental  Infections. — Constitutional 
effects  are  nearly  always  present  in  acute  infection.  They  are  evidenc- 
ed by  fever;  that  is,  raised  temperature,  quickening  of  the  pulse  and 
respiration  rates,  headaches,  flushing  of  the  face,  brightening  or  injec- 
tion of  the  eyes,  dry  hot  skin,  constipation,  highly  colored  urine  and, 
in  serious  cases,  perhaps  also  delirium  at  night. 

Leucocytosis  is  called  forth  in  nearly  all  cases  of  acute  infection  as  a 
protective  reaction  by  stimulation  through  the  toxins  of  the  bone 
marrow  and  other  places  where  leukocytes  are  formed. 

Discharges  are  especially  marked  in  the  critical  stage.  They  are 
profuse  sweating,  sometimes  hemorrhage  from  the  mucous  membranes 
and  often  diarrhea. 

All  these  constitutional  s^Tuptoms  may  be  slight  or  well  marked, 
according  to  the  physical  health  of  the  patient,  as  well  as  to  the  viru- 
lence of  the  infection.  In  serious  cases  the  absorption  by  the  blood 
circulation  may  become  so  extensive  that  we  speak  of  the  condition  as 
a  blood  infection,  or  septicemia.  While  we  generally  get  absorption 
both  of  bacteria  and  their  toxins  we  may  distinguish  various  typical 
conditions. 


216 


RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 


Bacteremia. — Bacteremia  is  a  condition  in  which  the  bacteria  are 
absorbed  from  the  original  seat  of  infection  and  circulate  and  grow  in 
the  blood.  If,  however,  the  bacteria  are  very  pyogenic  and  elaborate 
toxins  we  employ  usually  the  general  term  of  septicemia.  The  symp- 
toms are  those  already  described.  In  addition,  however,  there  is 
usually  a  chilly  sensation  or  actual  chills.  The  pulse  becomes  more 
rapid  and  progressively  weaker  and  the  temperature  rises  until  death 
occurs.     (See  Fig.  140.) 


DAY  OF 
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106 

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Fig.  140. — Puerperal  septicemia;  death.     (Ashhurst,  Episcopal  Hospital.) 

Pyemia.^ — This  blood  infection  is  generally  due  to  a  cluster  of  bacteria 
or  an  infected  blood  clot  entering  the  circulation.  It  then  usually 
lodges  in  a  capillary  and  the  bacteria  produce  suppuration  in  the  new 
location.  Thus  a  new  abscess  forms,  which  is  called  a  metastatic 
abscess.  This  may  be  located  in  any  part  of  the  body  and  is  fre- 
quently found  in  the  heart,  lungs,  liver  or  joints.  Suppurative  lesions 
in  the  bone  are  most  frequently  the  seat  of  the  primary  focus.  Fig. 
141  shows  a  temperature  chart  in  a  fatal  case  of  pyemia. 

Toxemia. — If  the  bacteria  remain  in  the  primary  lesion  and  only  the 
toxins  (both  true,  special  toxins,  and  the  poisons  produced  by  the 
biological  activity  of  pyogenic  bacteria)  are  absorbed  the  condition  is 
spoken  of  as  toxemia.  This  should  be  differentiated  from  auto- 
intoxication due  to  poisoning  by  non-bacterial  substances  such  as 
drugs  and  products  of  perverted  metabolism.  According  to  the  amount 
and  quality  of  the  toxins  and  the  reaction  of  the  individual  we  speak  of 
acute  and  chronic  toxemia.  The  latter  /ill  be  discussed  under  systemic 
effects  from  chronic  infections.  Acute  toxemia  cannot  very  well  be 
distinguished  from  septicemia  by  symptoms,  as  these  are  almost  the 
same.     It  yields  quickly  to  treatment,  however,  and  if  the  cause 


tnPECTED  TEETH  AS  A  SOURCE  OF  SYSTEMIC  DISEASE    21? 

(the  bacterial  focus)  is  removed  the  symptoms  usually  disappear 
promptly.  If,  however,  the  septic  focus  is  not  found  it  may  terminate 
in  septicemia. 


Fig.  141. — Temperature  chart  in  pyemia;  acute  osteomyelitis  of  calcaneum;  abscess  of 
brain;  death.     (Ashhurst,  Episcopal  Hospital.) 

Sapremia. — Sometimes  dead  tissue,  such  as  a  dead  pulp,  remains 
in  the  body  without  being  infected  by  pyogenic  bacteria.  Saprophytic 
bacteria  may  then  develop  and  form  ptomains  which,  when  absorbed, 


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Fig.  142. — Sapremia;  rapid  fall  of  temperature  after  evacuation  of  retained  secundines. 
(Ashhurst,  Episcopal  Hospital.) 

give  symptoms  similar  to  toxemia.  As  long  as  the  dead  tissue  remains 
there  will  be  constitutional  effects,  but  these  disappear  after  removal 
and  there  is  usually  a  prompt  restoration  of  health.    Fig.  142  shows  a 


218      RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 

temperature  chart  from  a  case  of  sapremia.  The  temperature  fell 
immediately  after  removal  of  the  dead  tissue. 

Systemic  Effects  from  Chronic  Dental  Infections. — In  chronic 
infections  lesions  such  as  have  already  been  described  often  start  and 
persist  for  a  long  period  without  local  symptoms  and  we  rarely  get 
acute  general  manifestations,  such  as  fever  and  other  symptoms  con- 
nected with  septicemia  due  to  acute  infection.  It  is  now  conceded, 
however,  by  most  pathologists  of  this  country  that  a  number  of  general 
diseases  are  caused  by  the  continued  absorption  of  bacteria  or  their 
poisonous  products  from  such  a  chronic  inflammatory  focus.  This 
transportation  of  an  infection  from  the  primary  lesion  to  another  place 
is  spoken  of  as  focal  infection. 

The  Focus. — ^The  focus  is  the  name  given  to  the  primary  infection, 
from  which  bacteria  or  their  toxins  may  be  transported  to  other  parts 
of  the  body.  It  may  be  found  in  any  part  of  the  body,  but  the  nose 
or  throat  and  adjacent  sinuses,  the  oral  cavity,  the  alimentary  canal, 
and  the  genito-urinary  system  are  the  parts  in  which  foci  are  found  most 
frequently.  Foci  are  not  always  apparent  and  are  often  only  recog- 
nizable after  a  most  careful  examination  by  the  specialist. 

Oral  Foci. — It  is  a  mistake  to  spread  the  impression  that  diseases 
of  the  mouth  and  teeth  always  play  a  predominant  part,  as  much  as  it  is 
a  mistake  to  think  that  the  teeth  and  their  investing  tissues  are  organs 
apart  from  the  rest  of  the  body  reacting,  for  some  mysterious  reason, 
differently  from  the  rest  of  the  human  organism.  Various  oral  lesions 
of  infectious  origin  have  already  been  described.  The  blind  abscess  or 
dental  granuloma  among  these  is  the  most  frequent  cause  of  systemic 
disease,  but  also  pulp  infection,  pyorrhea  and  other  bone  infections 
of  the  jaws  which  are  of  less  frequent  occurrence  may  play  an  important 
part.  The  bacterial  flora  of  the  mouth  includes  not  only  a  large  number 
of  saprophytes  which  live  on  dead  tissue,  but  also  an  extensive  variety 
of  the  pyogenic  organisms,  among  which  especially  prominent  are  the 
different  types  of  streptococci,  the  staphylococci,  pneumococci  and 
micrococcus  catarrhalis. 

Mode  of  Distribution  of  the  Infection  from  Oral  Foci. — Dental 
abscesses  with  fistulse  and  pus  pockets  discharging  into  the  mouth 
furnish  a  continual  supply  of  infectious  organisms  which  may  cause 
diseases  of  the  throat,  lungs  and  mucosa  of  the  alimentary  canal. 
From  a  deep-seated  focus  with  no  outlet  infection  may  take  place 
through  the  lymph.  There  are  two  groups  of  lymph  glands  which 
drain  the  jaws  and  teeth.  The  submental  glands  take  care  of  the  region 
of  the  lower  incisor  teeth.  The  three  submaxillary  lymph  glands  on 
each  side  drain  the  rest  of  the  teeth  and  their  investing  tissue.  All 
are  tributaries  of  the  lymph  nodes  of  the  neck.  These  glands  are  hardly 
noticeable  when  normal,  but  in  acute  infections  they  become  enlarged 
and  very  tender  to  touch.  In  chronic  infections  they  may  also  become 
enlarged,  but  are  harder  and  not  painful  on  palpation.  The  lymph 
vessels  may  also  become  involved  and  in  this  case  we  speak  of  the 


INFECTED  TEETH  AS  A  SOURCE  OF  SYSTEMIC  DISEASE    219 

condition  as  lymphangitis.  The  lymph  glands  are  more  liable  to  be 
enlarged  in  children,  but  l\Tnphatic  infection  is  not  at  all  rare  in 
adults.  The  most  important  path  of  absorption,  however,  is  through 
the  circulation.  Acute  infections  always  cause  more  or  less  involve- 
ment of  the  general  system,  but  also  in  chronic  infections  the  disease  is 
rarely  entirely  localized.  Bacteria,  or  the  toxins  formed  by  bacterial 
absorption,  or  both,  are  taken  up  by  the  blood  stream  in  the  focus, 
which  is  always  very  rich  in  primitive  vessels*  causing  a  bacteremia  or 
chronic  toxemia.  The  result,  however,  does  not  cause  cross  s,^^Ilptoms, 
as  in  acute  septicemia,  but  is  of  so  mild  a  character  that  the  patient's 
health  may  be  considerably  undermined  before  any  marked  effect  is 
noticeable. 

Secondary  Lesions.^ — ^The  bacteria  or  toxins  taken  up  by  the  blood 
may  be  carried  to  any  part  of  the  body  by  the  circulation  and  produce 
new  disease,  or  secondary  lesions.  The  type  of  secondary  disease  and 
the  part  affected  depend  upon  a  great  many  factors.  Predisposing 
causes  and  debilitating  diseases  are  very  important,  while  traumatic 
injury,  exposure  to  fatigue,  malnutrition,  pregnancy  and  other  con- 
ditions which  lower  the  resistance  give  opportunity  for  bacterial  inva- 
sion. The  varieties  of  bacteria,  of  course,  probably  have  tendencies 
toward  growth  in  certain  tissues  and  according  to  Rosenau's  latest 
studies,  members  of  the  same  type  may  develop  affinities  for  certain 
tissues.  Streptococci  taken  from  an  infected  heart  muscle  would,  if 
injected  into  the  blood  stream  of  another  animal,  again  elect  to  invade 
the  tissues  of  the  heart. 

Secondary  diseases  are,  however,  also  caused  by  absorption  of  bac- 
terial toxins  only.  While  these  may  not  be  of  sufficient  strength  to 
cause  acute  toxemia  they  can,  in  susceptible  patients,  cause  serious 
disturbances,  both  general  and  local.  Especially  delicate  tissues  are 
affected  so  that  physical  discomfort  and  mental  depression  may  result. 

Establishing  Proof  of  Systemic  Infection. — Often  it  is  difficult  to 
determine  whether  absorption  takes  place  from  suspicious  teeth. 
As  a  rule  there  is  little  doubt  as  to  what  should  be  done  with  infected 
teeth,  from  a  purely  dental  point  of  view,  or  even  simply  for  the  sake  of 
cleanliness.  No  one  who  has  studied  the  tooth  and  bone  pathology 
of  conditions  caused  by  old  pus-soaked  teeth,  or  who  has  experienced 
the  odor  of  one  which  has  been  removed,  will  hesitate  to  recommend 
extraction.  There  are,  however,  cases  where  we  might  recommend 
more  conservative  treatment  if  we  were  sure  that  no  absorption  was 
taking  place. 

Two  tests  are  available  to  decide  whether  absorption  of  bacterial 
poisons  has  occurred.  One  is  a  blood  test,  the  other  a  skin  test,  such 
as  that  used  in  testing  for  food  poisoning.  In  conjunction  with  Dr. 
Lawrence  of  Boston  I  have  experimented  with  these  tests.  The 
following  is  an  example. 

Mr.  G.,  a  chauffeur,  had  been  unable  to  drive  a  car,  on  account  of 
pain  in  his  back  and  shoulders.    Roentgen  pictures  of  his  teeth  (Figs. 


220 


RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 


143  to  152)  showed  many  devitalized  teeth  and  several  abscesses,  (marked 
A,  B,  C  and  D) ;  also  a  pus  pocket  (marked  E),  and  careful  examination 


Fig.  143 


Fig.  144 


revealed  no  other  possible  cause  for  his  condition.  The  blood  test, 
known  as  the  complement-fixation  test,  showed  a  reaction  to  two  types 
of  streptococci,  the  toxins  of  which  were  being  absorbed.    The  skin 


Fig.  145 


Fig.  146 


test  was  positive  to  the  same  organisms.  The  abscessed  teeth  were 
extracted,  cultures  were  made  from  each,  and  again  pure  cultures  of 
the  same  organisms  were  obtained.    The  patient  improved  so  much 


Fig.  147 


Fig.  148 


after  removal  of  the  focus  that  he  was  soon  able  to  go  to  work  and 
is  now  driving  a  truck. 


INFECTED  TEETH  AS  A  SOURCE  OF. SYSTEMIC  DISEASE    221 

General  and  Special  Diseases  which  may  Originate  from  Oral  Infections. 

In  the  following  list  are  enumerated  some  of  the  special  and  general 
diseases  which  may  have  their  origin  in  the  oral  cavity.  It  should  be 
clearly  understood  that  all  these  conditions  may  arise  from  a  focus  in 
any  part  of  the  body  and  that  diseases  of  the  teeth  are  not  the  only 
etiologic  factors,  nor  even  the  most  important  ones.  In  compiling 
this  list  the  writer  has  aimed  to  include  only  such  diseases  as  are  at 
present  generally  conceded  to  be  caused  by  focal  infection. 


*   ^   ^ 


Fig.  149 


Fig.  150 


Laryngology,  Rhinology  and  Otology. — Maxillary  sinusitis  in  its 
various  clinical  forms  is  quite  often  caused  by  dental  infections. 
However,  in  cases  which  are  clearly  of  nasal  origin  infected  and  devi- 
talized teeth  may  become  a  contributary  cause  which,  if  not  removed, 
will  prevent  complete  recovery.  Tonsillitis  and  pharyngitis  may  occur 
from  pus  discharged  into  the  mouth.  Ear  infection,  such  as  acute 
otitis  media  or  chronic  purulent  inflammation  of  the  middle  ear  and 
tympanum  may  be  caused  by  direct  invasion  through  the  Eustachian 


Fig.  151 


Fig.  152 


tube,  or  the  infection  may  be  transported  by  the  circulation.  Pain  in 
the  ear,  so-called  otalgia  dentalis,  is  frequently  only  a  reflex  pain 
from  some  cause  in  or  about  the  teeth. 

Ophthalmology. — Disturbances  in  the  eye  may  be  brought  about  by 
nerve  irritation,  or  through  hematogenous  or  direct  infection.  Infec- 
tious conjunctivitis  in  children  is  often  caused  by  rubbing  the  eyes 
with  the  fingers,  which  have  been  put  into  the  mouth  to  feel  an  aching 


222      RELATION  OF  ORAL  INFECTIONS  TO  HEALTH 

tooth,  which  discharges  pus  through  a  fistula.  The  pus  may  get  on  the 
child's  finger  and  be  brought  into  direct  contact  with  the  eyes.  Hema- 
togenous infection  may  cause  infection  of  other  parts  of  the  eye,  such 
as  iritis  and  retrobulbar  neuritis. 

Pediatrics. — Children  are  frequently  victims  of  focal  infection  caus- 
ing grave  and  sometimes  irremediable  conditions,  such  as  heart  disease 
(endocarditis),  kidney  disease  (nephritis)  and  acute  inflammation  of 
the  joints.  Acute  or  chronic  l^TQphadenitis  is  also  a  common  occur- 
rence in  children. 

General  Medicine. — Septicemia  and  pyemia  may  be  caused  by  infec- 
tions from  the  teeth,  but  are  of  comparatively  rare  occurrence.  Tox- 
emia, however,  is  more  frequently  observed.  Many  obscure  troubles 
are  due  to  absorption  of  a  small  amount  of  toxin.  Such  symptoms 
may  be  fatigue  disproportionate  to  the  slight  exertion  occasioning  it, 
inability  to  do  the  accustomed  day's  work,  mentally  or  physically, 
benumbed  mental  activity,  requirement  of  an  abnormal  amount  of  rest, 
loss  of  weight,  grayish  or  sallow  skin,  and  a  rise  in  the  temperature  in 
the  afternoon  or  evening.  A  perfectly  healthy  person  may  be  able  to 
eliminate  a  certain  amount  of  infection,  but  sooner  or  later  more  serious 
results  are  apt  to  occur.  Lowering  of  the  body  temperature  by 
exposure  to  cold  or  wet  may  give  rise  to  more  or  less  vague  rheumatic 
conditions  in  the  muscles,  (myositis),  joints,  (arthritis),  or  nerves, 
(neuritis) .  Cases  of  acute  multiple  arthritis  from  dental  infections  are 
not  uncommon  and  usually  improve  rapidly  after  removal  of  the  focus. 
In  chronic  infections,  especially  arthritis  of  long  standing,  the  results 
are  not  so  gratifying.  The  joints  may  present  tissue  changes  which 
are  beyond  repair  from  an  anatomical  point  of  view.  The  removal  of 
the  focus,  however,  usually  relieves  symptoms  of  pain  and  swelling  and 
prevents  reinfection  from  this  cause. 

Endocarditis  and  nephritis  are  also  caused  in  the  adult  by  transported 
infection  from  a  focus.  In  heart  infections  there  is  the  additional 
danger  of  damage  due  to  absorption  of  toxins  from  any  infectious 
lesion,  not  necessarily  the  cause  of  the  disease. 

Gastro-intestinal  disorders  are  frequently  caused  by  pus  from  the 
nasopharynx  or  mouth  being  swallowed  into  the  stomach.  According 
to  many  writers  the  most  common  disturbances  are  septic  gastritis, 
appendicitis,  colitis  and  gastric  and  intestinal  ulcers. 

CoNCLpsiON. — ^The  lesson  to  be  learned  from  these  studies  is  the 
importance  of  laying  more  stress  than  ever  upon  the  preventive  side 
of  dentistry.  Preservation  of  the  dental  pulp  and  its  sequel,  preven- 
tion of  periapical  infection,  starts  at  an  early  age.  Preventive  dentistry 
should  begin  with  children  and  no  treatment  will  further  this  object 
more  than  the  excellent  work  of  the  dental  hygienist. 


CHAPTER  XI. 
DENTAL  PROPHYLAXIS. 

By  ALFRED  C.  TONES,  D.D.S. 

THE  CELL. 

In  order  to  appreciate  health  it  is  necessary  to  be  familiar  with 
the  facts  concerning  the  individual  cell,  and  the  effect  of  various  influ- 
ences upon  the  unit  must  be  studied  before  an  understanding  can  be 
had  of  the  action  and  influence  upon  the  cells  in  the  aggregate.  If 
a  drop  of  water  is  taken  from  the  side  or  bottom  of  an  aquariimi  and 
put  in  a  glass  under  the  microscope,  a  minute  jelly-like  mass  may  be 
seen.  Its  outer  circumference  slowly  changes  its  shape,  while  near  the 
center  there  is  a  very  minute  globule  termed  the  nucleus.  This  is 
the  lowest  and  simplest  form  of  animal  life  and  is  known  as  the  ameba. 
This  simple  cell  has  seven  distinct  properties.  It  may  extend  its 
wall  in  projections  like  false  feet,  or  protuberances,  or  may  flatten 
itself  out  in  a  long  line,  therefore  it  has  the  property  of  elongation. 
When  irritated  by  being  brought  into  contact  with  dilute  acid  it  will 
contract  into  a  round  form;  hence,  it  has  the  property  of  contraction. 
These  two  properties  give  it  its  power  of  motion.  It  appreciates  the 
presence  of  irritants,  of  food  and  of  thermal  changes,  therefore  it  has 
the  power  of  sensation.  It  can  digest  food  and  discard  waste  tissue, 
therefore  it  must  have  the  properties  of  secretion  and  elimination. 
The  cell  and  nucleus  have  the  power  of  dividing  themselves  in  two, 
thereby  forming  two  cells.  It  has  the  power  of  reproduction,  and  the 
new  cells  have  the  property  of  growth. 

When  all  of  these  functions  or  properties  of  this  simple  cell  are  work- 
ing normally,  the  ameba  is  in  a  state  of  health  or  balance.  Rob  it 
of  one  or  more  of  its  properties  and  it  is  diseased.  Stimulate  the  cell 
by  applying  certain  agencies  and  its  motions  become  more  rapid,  it 
consumes  its  food  more  rapidly,  it  will  subdivide  and  reproduce 
itself  more  rapidly.  A  greater  stimulant  will  cause  a  still  greater  activ- 
ity, but  if  this  is  continued  the  cell  soon  becomes  exhausted  and  par- 
alyzed from  exertion  and  the  ultimate  result  will  be  death.  The  reverse 
takes  place  under  sedation  produced  by  applying  cold.  The  motions 
become  slower,  also  digestion  and  reproduction.  If  the  temperature 
is  dropped  too  low,  the  cell  dies.  Pollute  the  water  or  rob  it  of  its 
oxygen  and  the  cell  dies.  Cell  life  is  maintained  chiefly  by  a  chemical 
process  of  oxidation.  It  must  have  water  and  it  must  have  a  food  sup- 
ply to  replace  the  lost  substance  which  is  gradually  being  utilized 


224  DENTAL  PROPHYLAXIS 

in  performing  its  various  properties  and  functions.  It  is  therefore 
apparent  that  cell  life  is  dependent  upon  oxygen,  water  and  food, 
a  proper  temperature  and  removal  of  waste  matter. 

Nature,  in  the  building  of  all  matter,  builds  from  the  unit.  Although 
the  atom  is  the  smallest  unit,  the  molecule  of  the  mineral  kingdom  and 
the  cell  of  the  animal  and  vegetable  kingdoms  are  the  general  bases 
for  study.  All  earthly  creations  visible  to  us  are  formed  on  this  one 
plan.  The  trees,  the  flowers,  the  grass,  the  mountains,  the  beach, 
the  sea,  all  animal  life,  including  man,  each  is  made  by  the  combining 
of  these  units,  all  working  with  an  intelligence  and  subject  to  chemical 
laws  far  beyond  our  comprehension. 

Why  it  is  that  the  contents  of  the  cell,  which  is  called  protoplasm 
and  which  appears  to  be  nothing  but  a  jelly-like  mass,  has  the  property 
of  manifesting  life  and  intelligence,  is  difficult  to  understand.  This 
substance  can  be  analyzed  and  even  the  proportion  of  its  elements 
estimated,  yet  what  unseen  force  imbues  it  with  energy  and  intelli- 
gence and  what  becomes  of  this  life-giving  power  when  the  cell  dies 
and  disintegrates,  is  not  known.  Cell  action  can  be  studied,  and  the 
cell  can  be  supplied  with  the  essentials  for  growth  and  development.  It 
is  a  realized  science  that  in  animal  life,  certain  factors  properly  applied 
at  the  proper  age  can  greatly  develop  its  function  and  intelligence, 
the  same  as  in  vegetable  life,  but  it  cannot  be  explained.  It  is  known 
that  all  manifestation  of  life  and  of  intelligence  is  expressed  through 
this  matter  contained  within  the  cell. 

In  the  gradual  evolution  of  these  simple  cells,  like  the  ameba,  com- 
bining to  form  larger  and  more  complex  organisms,  it  is  found  that 
the  cells  choose  a  specialty  of  two  or  three  of  these  properties,  and  those 
whose  specialty  is  the  same  are  grouped  together.  As  animal  life 
develops  into  higher  planes  the  cells  become  more  proficient  in  their 
specialties,  until  in  man  is  found  the  greatest  variety  of  highly  special- 
ized cells  in  animal  life.  While  the  ameba  possesses  a  balance  of  seven 
properties,  some  of  the  specialized  cells  of  man  concentrate  on  but  one 
function.  It  may  now  be  seen  how  these  cells  of  man  that  have  under- 
gone a  slow  evolution  of  millions  of  years  to  reach  their  present  degree 
of  intelligence  are  reflected  in  this  low  and  simple  order  of  life — the 
ameba.  It  has  been  stated  that  the  ameba  has  seven  properties.  Its 
power  of  contraction  is  exemplified  in  the  muscle  cells  of  the  human 
body,  whose  specialty  is  contraction.  These  cells  are  capable  of 
wonderful  development  and  training.  The  finger  touch  on  the  piano 
keys,  the  surgeon  with  his  instruments,  the  dancer,  the  juggler,  the 
athlete,  the  artist,  and  the  artisan,  all  demonstrate  how  these  minute 
individuals  receive  impressions  from  the  brain  and  nerve  centers  and 
interpret  them  with  such  wonderful  intelligence.  The  nerve  cells 
specialize  on  the  transmission  of  sensation  and  vibratory  influences  to 
and  from  the  brain.  Digestion  and  elimination,  being  very  much  more 
complicated  in  higher  animal  life,  require  innumerable  cells  which 
perform  separate  functions — the  passing  on  of  food,  the  secretion  of 


THE  CELL  225 

fluid  for  its  solution  and  its  preparation  for  absorption.  In  the 
blood  stream  are  cells  floating  along,  each  intent  on  its  special  duty. 
The  liver,  with  its  cells  actively  engaged  in  preparing  the  waste  prod- 
ucts for  elimination  by  the  kidneys,  the  sweat  glands,  the  lungs, 
the  brain  (that  wonderful  terminal  station,  headquarters  for  all  orders) 
all  are  composed  of  these  specialized  units  working  together  like  so 
many  people  in  an  immense  city,  each  adding  his  mite  in  labor  and 
service  for  the  common  prosperity  and  health. 

The  intelligence  displayed  by  the  individual  cells  of  the  body  is 
the  marvel  of  scientific  investigators  in  physiology  and  pathology. 
Much  is  yet  wrapped  in  mystery  and  many  years  will  pass  before  some 
of  the  deep  problems  of  nutrition  and  the  hard-fought  battles  waged 
against  disease  will  be  fully  understood. 

When  the  body  is  abused  this  abuse  is  imposed  upon  millions  of 
intelligent  beings  who  do  their  utmost  to  offset  ignorance  and  wilful 
acts  by  patiently  combating  the  impositions  and  trying  to  correct 
and  repair  the  damage  wrought.  In  early  youth  the  cells  are  in  abun- 
dance and  the  supporting  structures  are  but  partially  formed.  In 
adult  life  the  work  of  the  cell  is  completed,  and  the  intercellular  struct- 
ure is  in  predominance.  The  great  period  for  structure  building  and 
for  the  guidance  of  proper  cell  development,  physically  and  intellect- 
ually, by  applying  scientific  factors  to  properly  infiuence  this  result, 
is  from  infancy  to  twelve  years  of  age. 

As  a  spider  spins  his  web  so  do  these  minute  cells  create  tissue 
to  aid  them  in  their  work.  The  individual  refiects  the  composite 
texture  and  make-up  of  the  aggregate  cells  of  the  body,  and  the  period 
for  molding,  refining  and  advancing  this  cell  development  to  its  highest 
plane  is  in  early  youth. 

Factors  for  Cell  Life. — ^The  scientific  factors  for  influence  are  numer- 
ous, but  there  are  a  few  that  stand  out  conspicuously.  First  of  all 
comes  pure  air,  for  cell  life  is  dependent  upon  constant  oxidation. 
Next  comes  a  proper  food  supply.  The  character  of  food  will  eventu- 
ally determine  the  character  of  the  cell,  and  as  the  body  is  physically 
composed  of  millions  of  cells,  the  food  supply  in  a  great  measure 
determines  the  character  of  the  individual.  This  is  exemplified  in  the 
glutton,  the  drunkard  or  the  savage.  What  is  eaten,  how  much  is  eaten, 
and  the  manner  in  which  it  is  eaten,  are  some  of  the  chief  factors  for 
health  balance.  The  question  of  food  values,  the  quantity  consumed 
and  the  importance  of  thorough  mastication  and  salivation  should  be 
a  study  for  all  hygienists. 

Next  comes  cleanliness,  for  if  disease  is  to  be  prevented  clean  food, 
clean  water,  clean  mouths,  clean  bodies  and  clean  environments  are 
necessary.  Mental  attitude  is  another  powerful  factor  and  should 
have  fourth  place.  Self-control,  optimism,  that  mental  poise  that  can 
discard  fear  and  worry,  that  holds  an  even  balance  under  varying 
circumstances  and  that  can  radiate  good  cheer  and  kindness  through 
their  health-giving  influences  to  every  cell  of  the  body,  are  elixirs 
15 


226  DENTAL  PROPHYLAXIS 

unequaled  in  the  building  of  the  character  as  well  as  in  regulating  a 
perfect  balance  and  functioning  of  the  entire  system. 

Although  heredity,  too,  plays  a  strong  part,  yet  the  first  four  factors 
named  can  greatly  modify  the  inherited  disposition  of  the  cells  if  wisely 
applied.  When  we  speak  of  coarse  natures,  we  speak  of  an  unfortunate 
inheritance  of  a  type  of  cell  life  that  might  have  been  greatly  softened 
and  modified  in  childhood. 

Exercise  is  also  exceedingly  important,  for  rest  means  rust  even  in 
animal  tissue. 

If  man  lived  what  is  termed  a  "natural"  existence,  which  means, 
in  other  words,  an  outdoor  and  primitive  life,  with  simple  coarse 
foods  and  work  or  exercise  in  the  open  air,  which  develop  the  animal 
side,  there  would  be  but  little  need  of  the  physician  or  the  dentist. 
The  coarse  food  would  mechanically  clean  and  polish  the  teeth  by 
friction,  and  the  out-of-door  exercise  or  work  would  cause  an  enforced 
breathing  which  would  mean  a  greater  intake  of  oxygen  to  burn  up 
the  slag  and  waste  products  in  the  system.  But  this  so-called  natural 
existence  is  not  possible  to  70  per  cent,  of  the  people  of  the  present 
day.  Their  very  existence  depends  upon  their  work  or  artificial  life 
in  the  cities,  and  the  yearly  increase  in  numbers  in  the  cities  rather 
proves  the  preference  for  the  city  over  the  country.  Therefore  this 
health  problem  of  city  life  must  be  solved.  The  factors  which  are 
productive  of  health  in  the  animal  life  must  be  substituted  artificially. 
The  passing  generation  cries  that  children  are  being  brought  up  too 
much  by  the  teaching  of  science  and  the  book  instead  of  in  the  good 
old-fashioned  way  of  letting  nature  look  after  them.  Take,  for 
example,  the  wild  rose  of  the  field  that  depends  upon  sunshine  and 
shade,  warmth  and  moisture  and  proper  soil  for  its  growth.  Nature 
does  not  and  cannot  always  supply  these  in  sufficient  degree  and  in 
proper  balance,  and  although  the  flower  is  beautiful  it  cannot  be  com- 
pared with  the  beautiful  rose  that  the  horticulturist  can  grow  when 
these  essentials  are  scientifically  and  artificially  supplied.  In  the  hot- 
house the  correct  temperature  can  be  maintained,  moisture  in  sufficient 
quantity  supplied,  sunshine  and  shade  regulated  at  will  and  fertilizers 
essential  to  stimulate  growth  added  to  the  soil.  The  work  of  Burbank 
in  scientifically  handling  vegetable  life  is  well  known  and  our  modern 
methods  of  agriculture  and  fruit  raising.  The  wonderful  feats  of  the 
horse,  hurdling,  running  and  trotting  are  due  in  great  measure  to  the 
scientific  training  by  man.  Many  instances  can  be  given  in  which 
nature  far  excels  her  natural  state  of  environments  if  the  essential 
factors  she  needs  are  supplied  artificially  and  scientifically  in  sufficie  it 
abundance  and  degree. 

And  so  it  is  in  the  growth  and  development  of  the  city  child,  and 
even  in  that  of  the  adult.  If  the  proper  factors  for  health  can  be  scien- 
tifically administered,  it  is  possible  to  grow  children  as  far  superior  to 
those  of  the  present-day  average  in  the  public  schools,  as  the  American 
Beauty  is  superior  to  the  wild  rose.  Man  has  had  his  progressive 
period;  woman  is  having  hers.    The  coming  one  belongs  to  the  children. 


THE  ALIMENTARY  TRACT  227 


THE  ALIMENTARY  TRACT. 

Before  confining  thought  and  attention  chiefly  to  the  teeth  and  their 
surrounding  tissues  and  considering  how  disease  may  be  prevented, 
a  few  simple  thoughts  regarding  the  body  must  be  presented,  that  it 
may  be  better  understood  how  important  a  part  the  mouth  plays  for 
health  or  for  disease.  There  is  no  better  way  of  doing  this,  perhaps, 
than  first  to  consider  a  country  with  its  many  people,  and  show  the 
factors  upon  which  it  is  dependent  for  health,  for  a  close  analogy  may 
be  drawn  between  the  life  of  a  simple  cell,  the  individual  and  the  nation 
as  a  whole.  Egypt  is  the  best  for  illustrating  this  thought,  for  here  is 
found  a  strip  of  life  running  through  a  region  of  apparent  death. 
Suppose  a  piece  of  green  cloth,  six  inches  wide  and  a  hundred  feet  in 
length,  was  laid  on  the  sands  of  the  seashore,  running  straight  up  on 
the  beach  from  the  water's  edge.  If  in  the  center  of  this  cloth  was  laid 
a  long  white  string  to  illustrate  the  river  Nile,  it  would  be  a  fair  repre- 
sentation of  Egypt.  The  Nile  runs  through  a  desert  and  the  water 
with  its  life-giving  power  has  created  a  living  body  close  to  its  borders. 
In  this  living  body  are  millions  of  people  who  are  dependent  upon  this 
alimentary  tract  or  river  for  their  existence.  Along  the  banks  may  be 
seen  the  water  buckets,  operated  by  the  natives  to  supply  their' fields 
and  gardens.  In  the  season  of  the  overflow  the  soil  is  soaked  with 
moisture,  the  crops  are  plentiful  and  there  is  ample  for  those  who  will 
work.  Canals  or  arteries  lead  from  the  river  bank  across  the  fields 
to  supply  life  and  growth  to  the  soil  that  would  be  desert  waste  with- 
out it.  If  it  were  possible  to  poison  the  source  of  the  Nile  so  that  its 
waters  carried  their  life-giving  properties  no  longer,  but  contained 
some  chemicals  that  were  destructive  to  plant  life,  or  sufficient  sewage 
to  poison  the  inhabitants,  Egypt  would  soon  cease  to  exist.  Just  in 
proportion  to  the  amount  of  poison  carried  down  the  river  would  the 
country  and  people  suffer  from  starvation  and  disease.  The  bodies 
of  all  animal  life  are  constructed  around  their  alimentary  tract.  The 
lowest  forms  of  cell  life  when  changing  to  a  higher  organism,  find  it 
essential  to  develop  first  a  mouth  and  digestive  tract,  for  the  intake 
of  food  is  of  first  importance  with  all  material  life.  The  body  with 
its  millions  of  cells  is  dependent  upon  the  flow  of  nourishment  through 
the  alimentary  tract  and  as  the  individual  lives  and  feeds  so  will  his 
body  thrive  or  deteriorate.  The  mouth  is  the  vestibule  or  gateway  to 
the  whole  system.  All  the  nourishment  and  food  supply  to  the  body 
must  pass  through  this  one  portal.  The  placing  of  the  food  in  the 
mouth  is  a  voluntary  action  and  it  can  be  controlled  as  long  as  it 
remains  there,  but  the  moment  it  is  swallowed  it  is  beypnd  voluntary 
control  and  is  sent  on  the  mysterious  journey  called  digestion,  absorp- 
tion and  assimilation. 

Assuming,  first,  that  the  food  eaten  is  clean  and  pure  and  above 
criticism,  and  enters  a  clean  mouth,  is  properly  masticated  and  swal- 
lowed, digestion  take  place  normally,  provided  the  mental  9,ttitude 


228  DENTAL  PROPHYLAXIS 

be  one  of  tranquillity  during  this  period.  If  the  mind  is  excited  or 
irritated,  it  will  send  depressing  messages  throughout  the  body  and 
the  process  of  digestion  is  retarded  and  disturbed. 

Under  such  clean  conditions  the  normal  processes  of  digestion  can 
take  place  with  a  minimum  amount  of  effort  and  energy  being  expended 
by  the  tissues  in  their  work,  and  the  product  after  digestion  is  fit  for 
the  blood  stream  to  offer  to  the  cells  of  the  body  the  nourishment  they 
need  to  perform  properly  their  respective  functions.  But  the  reverse 
situation  exists  regarding  the  mouth.  The  food  may  be  clean  and  pure 
but  the  mouth  unclean. 

Decomposing  Food  Debris. — In  discussing  the  harmful  effects  of 
decomposing  food  in  the  mouth,  the  subject  cannot  be  better  presented 
than  by  giving  some  of  the  thoughts  of  Dr.  E.  C.  Kirk  from  a  paper 
read  by  him  in  Providence,  R.  I.,  October  16,  1900,  and  published  in 
the  Dental  Cosmos  in  May,  1901,  entitled  "Some  Considerations 
Relative  to  the  Infant  Mouth." 

Regarding  the  artificial  feeding  of  infants  he  refers  to  the  training 
of  the  nurse  to  sterilize  the  milk  and  feeding  apparatus  in  order  that 
the  milk  shall  be  delivered  to  the  child's  stomach  free  from  bacteria 
"which  when  present  in  the  food  supply  so  alter  its  composition  as  to 
reduce  its  nutritive  value  and,  what  is  still  more  important,  set  up 
decomposition  processes  within  the  alimentary  tract  of  the  infant 
which  are  direct  causes  of  irritation  and  disease  to  the  infant  organism." 

Great  care  having  been  taken  in  preparing  the  food  and  in  feeding, 
no  attention  was  paid  to  the  film  of  milk  left  in  the  mouth  after  feeding. 
It  is  apparent  that  if  fresh  milk  is  poured  into  a  bottle  that  has  con- 
tained sour  milk,  infection  of  the  fresh  milk  will  immediately  take 
place.  In  the  feeding  process  the  sterile  milk  passing  over  the  infected 
surface  caused  by  the  residue  of  the  last  feeding  at  once  infects  the 
milk. 

Dr.  Kirk  says,  "There  can  be  but  one  result:  fermentation  of  the 
infected  fluid  begins  in  the  stomach;  putrefaction  of  the  proteid  ele- 
ments may  take  place;  quantities  of  gas  are  formed,  distending  the 
walls  of  the  stomach  and  intestines,  causing  pain  and  irritation, 
further  increased  by  the  irritating  effects  of  organic  acids  which  are 
end-products  of  this  fermentative  process.  Digestion  is  interfered  with 
or  arrested,  the  fermenting  mass  of  food  becomes  a  mechanical  as 
well  as  a  toxic  irritant;  diarrhea  sets  in,  the  whole  nutritional  process  is 
interfered  with  and  development  is  damaged  in  proportion  to  the 
length  and  severity  of  the  attack. 

"The  rational  remedy  for  this  state  of  affairs  is  clear  when  once  the 
conditions  to  be  therapeutically  met  are  understood.  In  the  first 
place,  removal  of  the  primal  cause  by  thorough  oral  cleanliness  and 
sterilization  in  so  far  as  that  end  may  be  obtainable.  This  may  be 
practically  accomplished  by  wiping  the  mucous  membrane  with  a 
saturated  solution  of  boric  acid  to  which  borax  has  been  added  in  the 
proportion  of  ten  grains  to  the  ounce,  or  with  a  very  dilute  solution 


THE  ALIMENTARY  TRACT  229 

of  phenol  sodique,  one-half  dram  to  the  ounce,  applied  on  a  cotton 
swab  or  with  a  soft  linen  handkerchief  wrapped  around  the  finger 
of  the  nurse." 

Now  apply  the  same  principle  to  the  growing  child  and  to  the  adult. 
The  teeth  of  a  child  between  the  ages  of  six  and  twelve  years  will 
present  surfaces  equal  to  twelve  to  sixteen  square  inches.  In  an  adult 
the  surfaces  will  average  about  twenty-five  square  inches.  This  means 
that  if  it  were  possible  to  peel  the  enamel  off  of  each  of  the  five  sur- 
faces of  each  tooth  and  place  them  side  by  side  they  would  cover  a 
piece  of  glass  three  and  one-half  inches  square  in  the  case  of  the  child, 
and  in  that  of  the  adult  a  piece  about  five  inches  square.  This  will 
give  a  rough  idea  of  the  amount  of  surface  presented  in  the  mouth  to 
permit  of  the  retention  of  a  certain  quantity  of  food  that  must  decom- 
pose unless  it  is  removed.  The  more  perfect  the  teeth  regarding 
form,  occlusion  and  enamel  surface,  the  more  self-cleansing  they  are, 
and  proportionately,  the  amount  of  food  so  retained  is  comparatively 
small.  The  mouths  that  present  such  ideal  conditions  are  rare,  espe- 
cially among  those  who  are  born  and  live  in  the  cities.  Where  the  teeth 
are  irregular  in  shape  and  position,  are  decayed  and  broken  down,  the 
amount  of  food  that  remains  is  considerable  and  the  volume  of  decom- 
posing material  constantly  being  swept  into  the  intestinal  tract  will 
eventually  breed  illness.  In  a  growing  child  such  mouth  conditions 
are  vicious.  "Suppose,"  said  a  prominent  educator  in  dentistry, 
"that  a  prescription  was  given  to  a  mother  by  a  physician,  to  mix, 
with  each  meal  that  the  child  ate,  a  half-spoonful  of  garbage.  Would 
she  carry  out  such  a  prescription,  and  if  she  did  and  the  child  became 
ill,  would  not  the  physician  be  liable  for  damages?"  And  yet  in  reality 
that  is  what  is  taking  place  in  the  average  mouth  of  the  children  in 
our  public  schools  and  in  the  mouths  of  the  great  working  classes. 
This  constant  drain  of  poison  into  the  intestinal  tract  in  child  life 
causes  an  intestinal  indigestion  where  bacterial  products  are  absorbed 
into  the  system  and  produce  fevers,  headaches,  eye-strain,  anemia, 
malaise,  constipation,  and  dizziness.  Nature  finally  takes  away  the 
child's  appetite  and  forces  it  to  bed  until  a  good  house-cleaning  of  the 
body  can  be  accomplished. 

These  poisons  from  the  mouth  are  insidious  and  slow  in  action. 
Many  can  and  do  withstand  them  for  years,  but  as  the  constant  drop- 
ping of  water  will  wear  away  the  stone,  so  will  the  products  of  decom- 
posing food  in  the  mouth  soon  destroy  good  digestion  and  undermine 
the  system. 

Vaughn  and  Novy,  in  their  book  entitled  Cellular  Toxins,  say, 
"The  effect  of  a  chemical  compound  upon  the  animal  body  depends 
upon  the  conditions  under  which  and  the  time  during  which  it  is  admin- 
istered. Thirty  grains  of  quinine  may  be  taken  by  a  healthy  man  dur- 
ing twenty-four  hours  without  any  appreciable  ill-effect,  yet  few  would 
be  willing  to  admit  that  the  administration  of  this  amount  daily  for 
months  would  be  wise  or  altogether  free  from  injur\\     In  the  same 


230  DENTAL  PROPHYLAXIS 

manner  the  administration  of  a  given  quantity  of  a  bacterial  alkaloid 
to  a  dog  or  a  guinea-pig  in  a  simple  dose  may  do  no  harm,  while  the 
daily  production  of  the  same  substance  in  the  intestine  of  a  man  and 
its  absorption,  continued  through  weeks,  and  possibly  years  may  be 
of  marked  detriment  to  the  health." 

It  must  be  borne  in  mind  that  the  manifestation  of  sickness  does 
not  come  from  the  presence  of  bacteria,  but  from  the  poisons  generated 
by  the  bacteria. 

'  Abbott  in  his  book  on  The  Principles  of  Bacteriology,  quotes  Roux 
and  Yersin  who  claim  that  the  potencies  of  the  poisons  that  have 
been  isolated  from  cultures  of  Bacillus  diphtherise  have  been  determined 
by  experiments  upon  animals,  and  it  has  been  found  that  0.4  milli- 
gram is  capable  of  killing  eight  guinea-pigs.  Please  remember  that 
four-tenths  of  a  milligram  represents  but  y-g-Q  part  of  a  grain.  Aside 
from  the  products  of  decocnposing  food  in  unsanitary  mouths  we  must 
seriously  consider  how  much  of  the  bacterial  poisons  may  be  generated 
in  such  mouths  daily  by  the  millions  of  microorganisms  present,  and 
whether  these  poisons  are  not  of  sufficient  quantity  eventually  to 
weaken  the  organism  and  render  the  body  susceptible  to  infection 
from  the  pathological  group  of  microorganisms.  In  the  battle  being 
waged  against  tuberculosis,  this  feature  will  be  given  much  impor- 
tance, and  the  day  is  not  far  distant  when  some  scientist  will  be  able 
to  compute  with  a  reasonable  degree  of  accuracy  how  much  bacterial 
poison  can  be  generated  in  twenty-four  hours  in  a  mouth  containing 
decayed  teeth  and  food  debris. 

Bacterial  Propagation. — In  considering  the  products  of  decomposing 
food  with  their  detrimental  action  on  the  system,  their  action  upon 
the  human  mouth,  than  which  there  is  no  better  breeding  ground  for 
germ  life,  must  also  be  considered.  The  mouth  is  an  ideal  incubator, 
for  here  we  find  all  of  the  essentials  for  the  propagation  and  develop- 
ment of  these  microorganisms.  The  right  temperature,  sufficient 
moisture,  air,  darkness  and  a  menu  to  choose  from  that  would  tempt 
any  member  of  this  large  family.  Germ  life  is  comparatively  harmless 
when  robbed  of  a  food  supply,  but  give  it  a  pabulum  upon  which  to 
feed,  develop  and  multiply,  and  it  becomes  active  and  virulent.  It 
must  be  borne  in  mind  that  all  mucus-lined  tracts  of  the  body  have 
their  flora  of  microorganisms  and  that  the  individual  must  live  among 
them,  that  the  few  friendly  ones  are  company,  but  that  too  many  are 
a  crowd,  and  that  in  this  crowd  are  our  enemies  who  feed  upon  the 
host  if  they  but  get  a  chance. 

An  unclean  mouth  means  an  increased  number  of  bacteria,  and 
with  increased  numbers  come  increased  dangers  from  infection.  The 
cavities  of  decayed  teeth  harbor  millions  of  these  mischief-makers, 
as  do  also  the  food  debris  and  calcareous  deposits  around  the  necks 
of  the  teeth.  They  may  enter  the  mouth  in  a  very  subdued  state, 
but  under  these  favorable  environments  they  soon  multiply  rapidly. 
The  usual  order  is  to  consider  their  activity  and  growth  in  unsani- 


THE  ALIMENTARY  TRACT  231 

tary  mouths,  but  this  will  be  reversed  and  the  medium  upon  which  they 
best  are  cultivated  in  the  laboratories  be  first  noted.  The  saprophytic 
class  are  those  which  exist  upon  dead  animal  or  vegetable  matter. 
The  parasitic  class  prefers  to  gather  its  nourishment  from  the  living 
host.  Many  of  both  classes  can  live  in  either  medium,  as  occasion 
demands. 

As  the  unorganized  ferment  of  gastric  or  intestinal  digestion  has 
the  power  of  changing  the  food  by  rearranging  its  elements,  usually 
by  a  process  of  hydration,  so  do  these  microorganisms  have  the  power 
of  breaking  down  tissue  or  decomposing  food  and  liberating  its  ele- 
ments in  their  search  for  carbon  and  nitrogen.  The  media  chiefly 
used  in  laboratories  for  cultures  of  microorganisms  are  bouillon  with 
agar-agar,  gelatin,  potato,  sugar  and  blood  serum.  If  these  are  kept 
at  the  right  temperature,  at  least  to  grow  mixed  cultures,  the  sapro- 
phytic class  is  quite  easily  developed,  for  the  extracts  of  beef,  sugars 
or  starches  form  an  attractive  pabulum.  Many  of  the  parasitic  variety 
can  also  be  grown  in  these  substances,  such  as  the  t^'phoid  bacillus, 
anthrax  and  others,  while  the  tubercle  bacillus  and  the  bacillus  of 
diphtheria  are  cultivated  in  the  blood  serum.  These  culture  media 
are  all  found  in  the  average  mouth,  even  to  the  blood  serum. 

When  the  teeth  are  decayed  the  amount  of  food  retained  in  the 
mouth  is  considerable,  but  especial  attention  should  be  called  to  con- 
gested and  bleeding  gums.  Here  is  an  ideal  medium  for  the  propa- 
gation of  infectious  germ  life,  and  it  is  not  only  the  cavities  in  the 
teeth  and  the  food  debris,  but  also  the  pernicious  condition  of  the  gum 
tissue  in  unsanitary  mouths,  especially  in  those  of  children,  that  is 
of  serious  concern.  The  germs  of  tuberculosis  or  of  diphtheria  can 
here  find  a  pabulum  for  their  propagation  and  development,  and 
undoubtedly  the  prevailing  condition  of  the  gingival  borders  of  the 
gums  is  one  of  the  most  important  steps  toward  infection.  The  bleed- 
ing and  congested  gums  and  the  decomposing  food  is  present,  all  that 
is  now  necessary  is  the  bacterium. 

All  observant  practitioners  will  readily  agree  to  the  statement  that 
mouths  that  contain  no  congested  areas  on  the  gingival  borders  of 
the  gums  are  exceptions.  The  dark  red  surfaces  will  bleed  upon  the 
slightest  pressure,  and  in  between  the  molars  and  bicuspids  where 
the  food  can  lodge  undisturbed  in  ill-kept  mouths,  even  a  slight  suc- 
tion will  start  a  copious  bleeding.  It  will  be  the  privilege  of  the  hygien- 
ist  to  note  in  the  treatment  of  each  new  patient  how  easily  the  gums 
will  bleed  upon  the  slightest  touch  of  instrument  or  porte  polisher.  The 
oozing  of  serum  and  blood  from  these  congested  points  is  of  equal 
importance  in  the  consideration  of  infectious  diseases  of  children  with 
the  decomposing  of  animal  and  vegetable  matter  found  in  the  decayed 
teeth  or  around  their  surfaces.  To  those  who  have  thoroughly  inves- 
tigated the  subject,  the  mouth  is  now  conceded  to  be  a  most  impor- 
tant field  for  bacterial  growth  and  systemic  infection. 


232  DENTAL  PROPHYLAXIS 

Tuberculosis. — One  of  the  greatest  battles  being  waged  in  preventive 
medicine  is  the  fight  against  tuberculosis,  and  this  fight  can  never  be 
won  as  long  as  the  mouth  conditions  of  the  mass  of  people  remain  as 
they  are  at  present. 

Scientific  investigators  are  agreed  that  tubercular  infection  frequently 
takes  place  through  the  tonsils  and  the  intestinal  tract.  If  this  is  true, 
the  bacilli  must  either  be  taken  in  with  the  food  supply  in  sufficient 
quantities  to  prove  dangerous,  or  they  must  find  lodgement  in  the 
mouth  in  decayed  teeth  and  congested  gum  surfaces.  With  unsanitary 
or  septic  conditions  existing  in  the  buccal  cavity,  many  bacteria  in  a 
state  of  virulency  are  constantly  drained  over  the  tonsils  and  into  the 
stomach.  Any  physical  depression  that  lowers  the  normal  resistance 
of  the  body  might  permit  of  the  invasion  of  these  pathogenic  organisms. 

The  medical  man  must  realize  that  the  gingival  borders  of  the  gums 
present  an  area  eight  times  greater  than  that  of  the  crypts  of  the 
tonsils,  and  that  in  the  average  mouth  the  gums  are  congested  and  bleed 
readily.  This  provides  the  ideal  culture  medium  for  the  tubercle 
bacilli.  Add  to  this  the  lowered  bodily  resistance  induced  by  the 
absorption  of  the  poisons  generated  by  the  immense  numbers  of 
bacteria  present  in  such  mouths,  and  it  makes  a  pathological  combina- 
tion that  seriously  hinders  the  medical  profession  from  making  any 
further  greater  reduction  in  the  mortality  from  this  disease. 

In  our  state  sanitariums,  where  the  tubercular  patients  are  segre- 
gated, the  mouth  conditions  are  deplorable.  It  is  true  that,  with 
plenty  of  fresh  air,  good  food  and  rest,  the  body  can  and  does  neutralize 
much  of  the  poison.  The  resistive  force  is  increased  and  the  disease 
pronounced  arrested;  the  word  cure  is  cautiously  used.  Could  the 
mouths  of  these  patients  be  made  sanitary  at  the  beginning  of  the 
treatment  and  rigid  rules  enforced  regarding  their  daily  care,  a  marked 
benefit  would  surely  be  observed.  When  the  mouth  is  clean  and 
wholesome  the  liability  to  this  form  of  infection  is  greatlj'  lessened . 

Systemic  Infection. — If  syphilis  and  wounds  of  the  surfaces  of  the 
body  are  excluded  there  are  but  three  ways,  ordinarily,  for  bacteria  to 
gain  entrance  into  the  blood  stream:  (1)  Through  tooth  passes,  such 
as  root  canals  and  diseased  pericemental  tissues;  (2)  through  the  tonsils 
and  (3)  through  the  intestines.  Infection  through  the  tonsils  or  the 
intestinal  tract  is  dependent,  in  a  great  measure,  upon  mouth  conditions. 

In  the  consideration  of  the  mouth  as  an  avenue  for  systemic  infection, 
the  attention  must  be  centered  upon  the  soft  tissues:  the  gums,  the 
pericementum  and  the  pulp,  for  these  are  the  tissues  chiefly  involved  in 
permitting  of  the  ingress  of  bacteria  into  the  lymphatics. 

Although  there  are  other  phases  of  dental  pathology  which  may 
produce  a  detrimental  action,  either  locally  or  systemically,  the  follow- 
ing three  conditions  are  most  prevalent  and  by  far  the  most  serious: 

(1)  Unsanitary  mouths,  with  decayed  teeth  and  decomposing  food; 

(2)  diseased  pericemental  tissues;  (3)  devital  and  infected  teeth. 
The  toxic  influence  of  unclean  mouths  is  especially  noticeable  in 


THE  ALIMENTARY  TRACT  233 

children,  frequently  producing  headache,  malaise,  dizziness,  imperfect 
vision,  slight  fevers,  diarrhea,  and  a  general  condition  of  malnutrition. 
And  these  minor  ailments  can  only  be  considered  as  secondary  to  the 
dangers  of  systemic  infections  which  are  frequently  produced  by  the 
actual  penetration  of  the  bacteria  through  the  mucous  membrane  of 
the  tonsils,  the  pharynx  and  the  intestines. 

The  next  factor  is  that  of  the  inflamed  and  diseased  tissues  support- 
ing the  teeth.  For  quite  a  number  of  years  dental  pathologists  have 
repeatedly  called  attention  to  the  dangers  of  these  pericemental  infec- 
tions as  a  probable  cause  of  systemic  disease,  and  since  Professor  Xoyes' 
definite  demonstration  of  the  network  of  l^-mphatic  vessels  in  the  peri- 
cemental tissues,  even  to  the  extreme  borders  of  the  gingiva,  there  can 
be  no  doubt  of  the  ingress  of  bacteria  through  these  vessels  into  the 
blood  stream,  and  their  subsequent  localization  in  some  of  the  other 
tissues  of  the  body.  There  is  much  scientific  and  clinical  evidence  to 
prove  that  pyorrhea  alveolaris  is  a  cause  of  systemic  infection  which 
may  be  produced  in  three  ways :  (1)  By  the  constant  exudation  of  pus 
in  the  mouth  and  thence  into  the  digestive  tract;  (2)  the  absorption, 
by  the  lymphatics,  of  the  bacteria  and  their  toxins  present  in  the 
deeper  areas  of  the  infected  tissues,  (3)  by  the  pumping  action  of  loose 
teeth  in  their  sockets  during  mastication,  forcing  bacteria  and  their 
toxins  into  the  capillaries  and  thus  into  the  blood  stream  itself. 

The  third  phase  for  consideration  is  proving  even  more  serious  than 
the  first  two,  for  the  a;-ray  has  revealed  to  us  infected  areas  within  the 
bone  tissue  at  the  apices  of  the  roots  of  the  teeth  which  we  have  hereto- 
fore never  suspected.  These  apical  infections  are  found  only  upon  teeth 
with  devital  pulps,  and  have  remained  so  long  undiscovered  because 
the  action  of  the  streptococcus  viridans  is  so  subtle  and  usually  produces 
no  local  soreness,  pain,  inflammation  or  pus. 

Our  research  workers  have  clearly  demonstrated  that,  under  certain 
conditions,  the  streptococcus  viridans  in  the  apical  infection  becomes 
aggressive  and  migrates,  developing  a  selective  action  which  varies  in 
affinity  for  different  tissues  of  the  body,  and  the  work  of  Billings, 
Rosenow,  Hartzell,  Thoma  and  others  has  proved  scientifically  that 
they  are  the  cause  of  many  of  the  most  serious  systemic  infections, 
especially  those  involving  the  hearty  the  kidneys  and  the  joints. 

The  death  of  the  pulp  is  due  chiefly  to  dental  caries  and  dental  caries 
is  so  exceedingly  common  that  it  is  difficult  to  find  two  school  children 
out  of  a  hundred  with  perfectly  sound  teeth,  and  even  in  early  child- 
hood our  school  children  average  seven  cavities  per  child.  Consequently 
there  are  few  young  people  who  escape  a  pulp  involvement  due  to  the 
penetration  of  the  bacteria  through  the  tooth  structure,  destroying 
this  delicate  and  sensitive  tissue.  Pulpless  teeth  are,  therefore,  so 
prevalent  that  it  is  the  exception  for  an  adult  over  thirty  years  of  age 
to  present  a  mouth  without  one  or  more  devital  teeth  which  already 
have,  or  which  may  develop  an  apical  infection.  The  work  of  the 
dental  hygienist  will  be  the  most  important  step  in  the  elimination  of 


234  '  DENTAL  PROPHYLAXIS 

systemic  infection  from  devital  and  infected  teeth,  for  her  field  of 
service  incl*udes  the  prevention  of  dental  caries  and  subsequent  pulp 
involvement. 

THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS. 

The  initial  cause  of  nearly  all  the  pathological  or  disease  con- 
ditions of  the  tissues  of  the  mouth  is  the  combination  of  microorgan- 
isms and  food  debris.  Bacteria  alone  or  food  debris  alone  would  be 
quite  harmless  in  the  mouth.  Nearly  all  germ  life,  in  order  to  become 
virulent,  or  its  presence  dangerous  or  even  objectionable,  must  have 
a  pabulum  upon  which  to  thrive.  It  is  therefore  dependent  upon 
some  attractive  food  supply  in  order  to  reproduce  and  multiply.  It 
is  known  that  foods  will  "spoil"  if  allowed  to  remain  in  a  warm  tem- 
perature for  any  length  of  time,  and  that  in  order  to  prevent  this  action 
the  germs  are  killed  by  boiling  or  heating  the  food,  tightly  sealing  it 
from  the  air  in  cans  or  jars  that  have  just  previously  been  boiled  or 
have  had  boiling  water  poured  into  them,  and  allowing  them  to  stand 
long  enough  for  their  surface  to  become  sterilized. 

Food  may  also  be  placed  where  it  will  be  kept  cold,  as  in  an  ice-box, 
where  the  presence  of  the  ice  will  so  reduce  the  temperature  that  the 
organisms  are  rendered  sluggish  and  inert. 

For  years,  many  efl^orts  have  been  made  to  find  some  drug  or  chemical 
that  could  be  used  in  the  mouth  to  kill  all  bacteria  and  thus  make  the 
mouth  sterile,  or  at  least  to  render  them  inert.  The  futility  of  even 
hoping  for  a  sterile  condition  of  the  mouth  has  long  since  been  demon- 
strated. It  is  impossible  to  sterilize  the  human  mouth,  and  even  if 
it  were  possible,  such  a  condition  could  be  maintained  but  a  very 
short  time.  Therefore,  if  it  is  impossible  to  keep  the  mouth  free  from 
bacterial  life,  and  as  the  combination  of  food  debris  and  bacteria  is 
the  chief  cause  of  dental  diseases,  is  there  not  some  way  in  which  the 
food  debris  can  be  thoroughly  removed?  It  is  upon  this  thought  that 
the  principles  of  prophylaxis  are  based. 

Dental  prophylaxis  is  that  scientific  effort,  either  operative  or  thera- 
peutic, which  tends  to  prevent  diseases  of  the  teeth  and  their  surrounding 
tissues.  Correcting  and  restoring  to  normal  function  all  abnormal 
or  pathological  conditions  of  the  teeth,  and  maintaining  that  normal 
condition,  is  a  prophylactic  procedure.  This  includes  practically  all 
the  operations  in  dentistry.  The  mere  filling  of  a  tooth  cannot  be 
termed  prophylactic  unless  the  operation  is  performed  with  a  knowl- 
edge and  skill  that  tends  to  prevent  future  decay  at  that  point  and 
that  will  restore  the  surface  of  the  tooth  to  normal  contour  and  normal 
function.  Crowns  and  bridges,  root-fillings,  approximal  fillings  with 
proper  contact  points,  and  smooth,  flush  margins,  the  correction  of 
malocclusion,  the  removal  of  all  calcareous  deposits,  polishing,  the 
instruction  in  the  home  care  of  the  mouth,  may  all  be  made  prophylactic 
if  properly  done. 


THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS  235 

The  Service  of  the  Dental  Hygienist. — The  dental  hygienist  must 
regard  herself  as  the  channel  through  which  the  knowledge  of  preventioji 
that  the  dental  profession  has  acquired  is  to  be  disseminated.  The 
greatest  service  she  can  perform  is  the  slow  and  painstaking  education 
of  the  public  in  mouth  hygiene  and  allied  branches  of  general  hygiene. 
The  education  and  training  of  dental  hygienists  does  not  aim  to  produce 
mechanical  operators.  An  unlimited  field  of  educational  and  preven- 
tive service  is  open  to  the  dental  hygienist  who  regards  herself  primarily 
as  a  hygienist  and  educator,  and  secondarily  as  a  prophylactic  operator. 

The  dental  prophylactic  operation  of  the  dental  hygienist  is  chiefly 
concerned  with  the  exposed  surfaces  of  the  teeth,  the  necks  of  the  teeth 
directly  under  the  free  margin  of  the  gums,  and  the  gum  tissue  itself. 
It  must  always  be  borne  in  mind  that  the  aim  of  the  dental  hygienist 
is  to  secure  extreme  cleanliness  of  the  mouth  in  an  effort  to  starve 
bacteria  and  render  them  inert,  and  it  is  to  this  end  that  the  cooperation 
of  the  patient  must  be  secured. 

It  will  be  found  that  the  average  mouth  presents  an  unsanitary 
condition  that  encourages  the  propagation  of  millions  of  microorgan- 
isms, and  is  a  menace  to  the  health  of  the  patient.  It  is  the  duty  of 
the  hygienist  to  be  kind  in  her  criticism  to  such  a  patient,  for  in  most 
cases  the  individual  is  not  responsible  for  this  deplorable  condition. 
The  ignorance  of  the  patient  regarding  the  proper  care  of  the  mouth, 
and  the  careless  operative  work  of  many  dentists  is  usually  responsible. 
It  will  be  found  that  the  great  majority  of  patients  are  eager  to  learn 
the  correct  care  of  the  mouth,  and  follow  instruction  faithfully  when 
they  are  once  enlightened.  After  these  unsanitary  mouths  are  seen  to 
develop  into  healthy  ones  under  prophylactic  skill  and  instruction, 
the  dental  hygienist  will  realize  that  the  service  she  may  render  to 
humanity  is  a  very  important  one. 

The  procedure  which  should  be  adopted  with  a  new  patient  may  be 
divided  into  three  parts:  (1)  The  examination  of  the  mouth;  (2)  the 
dental  prophylactic  treatment,  and  (3)  the  instruction  of  the  patient 
in  the  home  care  of  the  mouth. 

Examination  of  Adult  Mouths. — The  general  condition  of  the  teeth 
should  first  be  noted.  It  will  be  found  that  the  enamel  surfaces  are 
without  luster  and  are  covered  with  a  pasty  colorless  film.  The  necks 
of  the  teeth  are  stained;  calcareous  deposits  are  seen  on  the  lingual 
surfaces  of  the  lower  incisors  and  the  buccal  surfaces  of  the  upper 
molars.  All  of  these  conditions  can  be  corrected  by  the  hygienist, 
but  she  is  dependent  upon  the  aid  of  the  dentist  to  remedy  the  unsani- 
tary construction  of  fillings,  crowns  and  bridges.  At  this  point  all 
conditions  of  the  teeth  which  the  hygienist  believes  require  the  atten- 
tion and  cooperation  of  the  dentist  should  be  recorded  upon  a  chart. 
This  will  include  any  decayed  surfaces  which  she  may  note,  as  well  as 
cough  fillings  or  margins  of  fillings  that  are  extended  beyond  the  tooth 
surface  and  retain  food  debris.  It  will  be  necessary  for  the  dentist  to 
carefully  grind  and  polish  all  such  fillings  in  order  that  the  desired 


236  DENTAL  PROPHYLAXIS 

results  may  be  obtained  from  the  prophylactic  treatments.  A  record 
should  be  made  of  fillings  in  the  approximal  surfaces  if  there  is  sufficient 
space  to  permit  of  food  packing  down  between  the  teeth  to  injure  or 
inflame  the  gum  tissue.  New  fillings  with  proper  contact  points  are 
frequently  needed  to  remedy  this  condition. 

If  there  are  gold  crowns  or  banded  crowns  that  do  not  fit  tightly  to 
the  tooth  or  root  and  that  will  permit  the  end  of  the  explorer  to  pass 
between  the  root  and  the  band  or  crown,  it  may  be  taken  for  granted 
that  such  a  space  is  filled  with  decomposing  food  and  is  an  ideal  haven 
for  bacteria.  The  odor  arising  from  such  crowns  after  their  removal 
makes  one  realize  the  necessity  for  tight-fitting  bands  and  flush  joint 
operations.  Hygienists  will  come  to  loathe  the  average  gold  crown  and 
will  use  their  influence  against  their  insertion.  Many  of  them  are 
sources  of  systemic  infection  and  nearly  all  will  destroy  the  pericemen- 
tum around  the  tooth,  and  result  in  the  eventual  loss  of  the  tooth. 
Such  dentistry  is  a  serious  menace  to  public  health  and  has  undoubtedly 
been  the  cause  of  many  severe  illnesses  that  have  resulted  even  in  death. 
If  an  ill-fitting  gold  crown  is  placed  over  a  tooth  containing  a  live  pulp, 
it  is  but  a  question  of  time  when  the  bacteria  and  the  poisons  generated 
by  the  decomposing  process  of  the  food  debris  lodging  in  the  space 
under  the  crown  where  the  cement  has  disintegrated  and  washed  away, 
will  penetrate  the  dentin  and  infect  and  destroy  the  pulp.  Apical 
infections  from  teeth  carrying  gold  crowns  are  common.  It  would  be 
far  better  for  the  patient  who  could  not  afford  to  have  the  work  done 
properly,  to  have  such  teeth  extracted.  Ill-fitting  bridges  so  con- 
structed that  it  is  impossible  to  properly  remove  the  food  with  the 
brush  and  washes  will  badly  hamper  work  for  mouth  hygiene. 

It  is  not  necessary  to  know  the  details  of  the  work  of  construction 
of  crowns  or  bridges  or  of  fillings,  but  it  is  necessary  to  know  what 
constitutes  good  dentistry  and  sanitary  construction.  A  small  pimple 
on  the  gum,  termed  by  the  layman  gum-boil,  is  in  reality  a  fistula 
opening  from  an  alveolar  abscess.  The  attention  of  the  dentist  should 
be  called  to  these  fistulse. 

The  gum  tissue  should  now  be  examined.  The  term  congested  gums 
is  applied  to  enlarged  capillaries,  engorged  with  blood  and  having 
a  sluggish  circulation.  External  irritation  from  lack  of  use  and  func- 
tion in  the  mastication  of  proper  foods  is  usually  the  cause  for  this 
congestion.  The  deep  red  color  is  due  chiefly  to  the  sluggish  flow  of 
blood  laden  with  carbon  dioxid.  Perfect  metabolism  is  not  taking 
place  in  the  cells  of  this  tissue  and  the  waste  products  are  not  being 
carried  away  with  sufficient  rapidity.  Any  local  irritant  on  the  sur- 
face or  border  of  the  gums  will  produce  this  congestion,  and  the  mouths 
are  rare  that  do  not  contain  a  number  of  congested  surfaces. 

In  the  mouths  of  children  this  condition  is  also  produced  by  the  sharp 
edges  of  decayed  or  broken-down  teeth,  temporary  and  permanent, 
and  sufficient  blood  and  serum  ooze  from  these  blood-engorged  areas 
to  form  an  excellent  culture  medium  for  pathogenic  bacteria. 


THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS  237 

Every  organism  has  its  vulnerable  or  vital  area  which  if  sufficiently 
injured  will  eventually  cause  its  death.  The  tooth  is  no  exception  to 
this  rule.  Its  vulnerable  point  is  the  border  of  the  peridental  mem- 
brane directly  beneath  the  gingival  margin  of  the  gum  around  the 
neck  of  the  tooth,  and  this  must  be  carefully  safeguarded.  This 
membrane  forms  the  most  vital  part  of  the  foundational  structure  of 
the  tooth.  Upon  its  health  and  resistance  depend  the  function  and 
life  of  the  whole  tooth.  If  it  becomes  injured,  irritated  or  infected  at 
its  border  and  the  lesion  or  infection  is  neglected,  the  membrane  dies 
at  this  point,  and  in  dying  it  causes  the  death  and  absorption  of  a 
similar  area  of  the  alveolar  process  which  was  in  apposition  to  the 
affected  membrane.  This  means  a  space  or  so-called  pocket  under 
the  margin  of  the  gum  where  food  debris  can  find  lodgement  and 
where  bacteria,  well  out  of  the  currents  of  the  saliva  which  flow  freely 
around  the  teeth,  can  hold  a  tenable  position. 

The  rapidity  of  the  progress  of  death  and  absorption  is  dependent 
upon  the  resistant  force  contained  within  the  cells  of  the  membrane 
and  upon  the  virulency  of  the  attacking  microorganisms.  In  child- 
hood this  membrane  is  thick  and  highly  vascular  and  can  resist  almost 
any  invasion  of  bacteria  even  when  wounded,  if  not  too  seriously. 
In  adult  life  it  gradually  becomes  thinner,  its  blood  supply  is  lessened, 
and  as  age  advances  the  cells  lose  the  high  resistant  force  that  they 
possessed  in  youth;  and  if  the  person  is  in  what  we  call  a  run-down 
condition  physically,  from  improper  feeding  of  the  body,  unclean  envi- 
ronments, harmful  habits,  excesses,  or  from  any  cause  that  will  disturb 
the  proper  metabolism  of  the  tissue  by  disturbing  the  nutritive  or  the 
nervous  systems,  the  resistant  force  is  still  further  lowered  and  the  peri- 
dental membrane  and  the  surrounding  supporting  tissues  of  the  tooth 
become  easy  prey  to  the  invading  bacterial  host.  Although  it  will 
be  possible  to  raise  the  resistance  of  this  membrane  again  by  prophy- 
lactic treatment  and  training  of  the  patient  in  the  proper  methods  of 
artificial  stimulation,  it  can  readily  be  seen  that  it  is  far  more  desirable 
to  prevent  the  original  disturbance  at  the  neck  of  the  tooth  and  save 
the  patient  the  surgical  treatment  necessary  in  the  hands  of  the  den- 
tist in  order  to  get  control  of  this  much-dreaded  and  serious  condition 
of  absorption  and  infection  of  the  supporting  tissues  of  the  root  of 
the  tooth.  It  must  always  be  borne  in  mind  that  the  most  important 
part  of  the  tooth  is  the  root  and  any  irritation  of  the  gingival  border 
of  the  gum,  especially  in  adult  life,  is  a  menace  to  that  tooth  which  is 
in  closest  proximity  to  the  point  of  irritation. 

Before  operating  in  the  mouth  of  a  new  patient  the  hygienist  should 
make  sure  that  the  patient  has  removed  all  of  the  food  debris  from  the 
teeth  that  it  is  possible  to  remove  with  the  tooth-brush,  floss  silk  and 
mouth  wash.  It  is  never  the  duty  of  the  hygienist  to  operate  in  a 
mouth  that  contains  food  debris.  For  her  own  self-respect  and  for 
the  dignity  of  her  calling,  she  should  make  it  an  absolute  rule  never  to 
Start  an  operation  of  prophylaxis  when  the  patient  has  failed  to  clean 


238  DENTAL  PROPHYLAXIS 

his  teeth  of  food  debris  before  coming  to  her  department.  It  is  never 
her  duty  to  remove  food  debris  excepting  the  small  quantities  that 
roughened  surfaces  have  made  it  impossible  for  the  patient  to  remove. 
These  cases  will  require  some  diplomacy  on  her  part,  for  she  must  realize 
that  the  patient  has  not  intentionally  insulted  her  by  presenting  such 
an  unclean  mouth.  It  is  merely  that  he  has  never  been  taught  better. 
For  years  dentists  h^ve  consented  without  remonstrance  to  operate 
in  the  mouths  from  which  the  food  has  not  been  removed  from  between 
the  teeth,  and  it  will  be  one  of  the  missions  of  the  hygienist  toward  the 
uplift  of  the  dental  profession  to  teach  patients  that  they  must  not 
present  themselves  for  any  dental  service  whatsoever  unless  their 
teeth  have  been  thoroughly  brushed  and  flossed.  She  should  be  kind 
and  considerate  in  the  handling  of  such  cases,  and  explain  to  the 
patient  that  there  is  danger  of  infecting  the  gum  tissues  if  the  instru- 
ments are  used  around  the  necks  of  the  teeth  where  there  is  decompos- 
ing food,  and  that,  in  order  to  obviate  any  such  danger  it  will  be  neces- 
sary for  him  to  step  to  the  bowl  and  thoroughly  brush  and  rinse  his 
mouth  before  the  operation. 

A  stock  of  tooth-brushes  should  be  a  part  of  the  equipment  of  every 
dental  office  and  should  be  charged  up  against  the  expense  of  dental 
supplies.  The  cost  of  the  brushes  if  bought  in  quantities,  amounts  to 
but  little  when  we  consider  their  absolute  necessity  for  instruction,  and 
their  use  when  needed  under  these  conditions. 

Patients  soon  learn  the  rules  of  an  office  and  in  a  comparatively 
short  time  it  will  be  a  rare  thing  to  be  obliged  to  send  a  patient  to  the 
bowl  to  brush  his  teeth  before  the  prophylactic  treatment  can  be 
started.  Much  of  the  soreness  of  the  gums  after  these  treatments  in 
the  mouths  of  new  patients  is  due  to  crowding  some  of  this  infected 
material  under  the  gum  margin  with  the  instrument,  and  it  follows 
that  the  cleaner  the  necks  of  the  teeth  are  before  instrumentation,  the 
quicker  will  be  the  recovery  of  the  congested  gums  after  treatment. 

The  Prophylactic  Treatment. — ^In  considering  the  practical  work  of 
dental  prophylaxis  the  operation  in  the  mouth  of  the  adult  will  be  first 
described.  With  a  pledget  of  cotton  soaked  with  peroxide  of  hydrogen, 
the  necks  of  the  teeth  and  also  the  approximal  surfaces  should  be  bath- 
ed. The  boiling  of  the  peroxide  will  mechanically  aid  in  loosening 
minute  particles  of  food  debris.  After  rinsing  the  mouth  with  warm 
water  the  teeth  should  be  thoroughly  sprayed  on  all  their  surfaces  with 
compressed  air  and  an  atomizer.  The  air  pressure  should  be  at  least 
twenty-five  pounds,  so  that  it  may  have  enough  force  to  blow  the  spray 
with  sufficient  force  between  the  teeth  to  aid  in  this. mechanical  cleans- 
ing. It  makes  no  difference  what  liquid  is  used  in  the  atomizer  if  it  is 
harmless  and  has  a  pleasant  taste. 

Surfaces  of  the  Teeth.— It  must  be  remembered  that  in  this  work 
hygienists  are  not  to  cross  the  border-line  into  surgery.  The  laws  in 
all  states  prohibit  surgical  or  medicinal  treatment  by  any  but  graduate 
practitioners,    Therefore  the  entire  efforts  of  the  hygienist  are  to  be 


THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS  239 

confined  to  the  exposed  surfaces  of  the  teeth  and  the  area  directly  under 
the  free  margin  of  the  gum. 

The  base  of  the  crown  of  each  tooth  has  four  lines  or  boundaries. 
This  is  the  entire  field  for  the  use  of  the  instruments  unless  a  root  sur- 
face is  exposed.  It  can  be  readily  appreciated  what  a  slow  and  pains- 
taking piece  of  work  it  is  to  go  over  carefully  each  of  these  surfaces 
and  remove  all  of  the  deposits  of  tartar.  In  the  first  treatments  of 
neglected  mouths  the  deposits  are  likely  to  be  large  and  are  usually 
found  on  all  the  surfaces  at  the  necks  of  the  teeth.  It  is  impossible 
to  remove  all  of  these  deposits  at  one  sitting  without  subjecting  the 
patient  to  an  unnecessary  strain.  The  large  deposits  may  be  broken 
down  and  scaled  off  and  many  of  the  smaller  nodules  can  be  removed, 
but  it  is  quite  impossible  to  be  really  thorough  in  the  first  treatment. 
Again,  it  is  unwise  to  subject  patients  to  a  too  strenuous  session,  for 
if  they  are  timid,  they  are  apt  to  become  discouraged  by  the  long  and 
tedious  sitting.  It  is  far  better  to  arrange  two  sittings  of  an  hour  and 
a  quarter  to  an  hour  and  a  half  each  than  one  of  two  hours  and  a  half. 
If  the  appointment  is  made  for  two  hours,  the  balance  of  the  time  may 
be  spent  in  polishing  and  in  instruction  of  the  home  care  of  the  mouth. 

The  subject  of  calcareous  deposits  has  been  so  thoroughly  covered 
by  Dr.  Kirk,  that  it  is  unnecessary  to  go  into  it  very  deeply,  but 
attention  should  be  called  to  the  irritating  action  they  display  in 
their  porousness  in  absorbing  liquefied  debris,  therefore  forming  an 
excellent  retainer  for  bacteria.  It  is  absolutely  essential  for  the  health 
of  the  gums  and  the  roots  of  the  teeth  that  all  such  deposits  be  removed 
at  frequent  periods!  The  time  maj^  come  when  people  may  be  induced 
to  eat  the  proper  foods  in  proper  quantities,  then  this  deposit  will  be 
greatly  lessened,  but  until  this  goal  of  good  sense  is  gradually  reached, 
artificial  care  of  the  mouth  by  prophylactic  treatments  will  have  to 
be  resorted  to. 

Much  of  the  evil  from  the  forming  of  serumal  deposits  in  the  subgin- 
gival space  can  be  obviated  by  eliminating  the  congested  condition  of 
the  capillary  circulation  found  in  the  gum  tissue  of  the  mouth  of  the 
average  adult.  But  the  mouths  are  indeed  rare  in  which  no  new 
deposits  can  be  found  under  the  gingival  border  after  a  period  of  two 
months. 

System  for  Instrumentation. — In  order  to  perform  a  prophylactic 
operation  intelligently  one  must  work  by  system,  and  the  instru- 
mentation as  well  as  the  polishing  must  have  a  definite  starting-point 
in  the  mouth  and  should  always  proceed  in  the  same  given  direction 
over  the  surfaces  of  the  teeth  in  the  case  of  every  patient.  This  is 
necessary  for  thoroughness  and  also  in  case  of  interruption,  for  if  one 
will  but  note  mentally  the  last  tooth  being  worked  upon  before  leaving 
the  chair,  the  chain  will  remain  unbroken  upon  resuming.  It  matters 
little  what  system  is  finally  adopted,  but  the  one  here  suggested  is 
advocated  because  it  has  proved  very  practical, 


240  DENTAL  PROPHYLAXIS 

Lower  Jaw. — Beginning  on  the  lingual  surface  of  the  right  lower  last 
molar  at  the  gingival  line,  distolingual  angle,  instrumentation  proceeds 
mesially  until  the  lingual  border  of  the  left  lower  central  is  reached. 
The  same  direction  is  now  followed  but  the  line  of  operation  becomes 
distal  on  the  left  side,  still  keeping  on  the  lingual  surface  until  the 
distolingual  angle  of  the  left  lower  last  molar  is  reached. 

Again  starting  on  the  distobuccal  angle  of  the  left  lower  last  molar, 
the  instrumentation  proceeds  buccally  and  mesially  until  the  left 
lateral  is  reached,  where  from  this  point  the  operation  continues  on 
the  same  surface  to  the  distobuccal  angle  of  the  right  lower  last  molar. 


8  FINISH         1  START 


■,/P):         2    3  ((%^- 


The  following  cuts  are  taken  from  Plate  VI  of  the  American  System 
of  Dentistry,  and  will,  by  the  dotted  lines  and  arrows,  better  illus- 
trate the  directions  followed  as  just  described.  Fig.  153  represents 
the  teeth  of  the  lower  jaw  with  crowns  excised  at  the  gingival  border. 
These  cuts  will  illustrate  the  lines  to  be  followed  and  field  of  operation 
to  be  covered  by  the  dental  hygienist  with  the  instruments. 

As  shown  by  the  dotted  lines  in  Fig.  153,  this  first  use  of  the  instru- 
ments on  the  lower  teeth  covers  only  the  lingual  and  buccal  surfaces. 
By  working  along  on  the  same  surfaces  of  the  teeth  on  the  same  jaw, 
considerable  time  may  be  saved  by  not  having  to  change  instru- 
ments every  moment  or  two,  as  one  instrument  frequently  will  adapt 
itself  to  eight  teeth  before  it  will  be  found  necessary  to  change. 

After  the  deposits  have  been  removed  from  the  lingual  and  buccal 
surfaces,  attention  is  given  to  the  distal  surfaces.  Once  more  begin- 
ning on  the  distal  surface  of  the  right  lower  third  molar,  the  distal 


THE  PRINCIPLED  OF  DENTAL  PROPHYLAXIS 


241 


surface  of  the  right  lower  molars,  bicuspids  and  cuspid  are  carefully 
scraped.  Next  the  distal  surfaces  of  the  left  lower  cuspid,  bicuspids 
and  molars,  as  illustrated  in  Fig.  154.  One  instrument  will  usually 
adapt  itself  to  these  surfaces.     Next  the  mesial  surfaces  of  the  right 


4  -^-4 


-3 

3  -.5)- 


Fig.  154 


lower  molars,  bicuspids  and  cuspid,  then  the  mesial  surfaces  of  the  left 
lower  cuspid,  bicuspids  and  molars.  These  surfaces,  too,  ma}-  usually 
be  covered  with  one  instrument.  Lastly,  the  approximal  surfaces  of 
the  lower  incisors,  which  may  be  covered  with  two  instruments  (Fig. 
155). 


4 


R 


L 


Fig.  155 

Upper  Jaw.— On  the  upper  jaw  at  the  point  corresponding  with  that 
where  work  was  first  started  on  the  lower  jaw,  the  distolingual  angle 
of  the  right  upper  third  molar,  the  lingual  surfaces  of  the  superior  set 
16 


242 


DENTAL  PROPHYLAXIS 


are  cleaned  of  all  calcareous  deposits,  working  mesially  until  the  left 
central  is  reached,  then  distally  to  the  left  third  molar.    Again  start- 


ing  at  the  distobuccal  angle  of  the  left  upper  third  molar  the  buccal 
surfaces  are  gone  over,  working  mesially  to  the  right  central  then 


Fig.  157 


distally  to  the  right  third  molar  (Fig.  156).     Now  beginning  at  the 
right  third  molar,  the  distal  surfaces  of  the  right  molars,  bicuspids  and 


THE  PRINCIPLES  OF  DENTAL  PROPHYLAXIS 


243 


cuspids  are  scraped.  Next  the  distal  surfaces  of  the  left  cuspid,  bicus- 
pids and  molars  (Fig.  157).  In  the  same  order  the  mesial  surfaces 
are  gone  over,  leaving  the  approximal  surfaces  of  laterals  and  centrals 
until  the  last  (Fig.  158). 

If  this  briefly  outlined  system  is  followed  there  will  be  but  little 
chance  that  the  deposits  may  escape  the  play  of  the  instruments. 

There  is  nothing  that  instils  a  greater  confidence  in  the  operator, 
in  the  mind  of  the  patient,  than  the  gentle  touch  of  his  hand  and  the 
instruments.  The  very  first  requisite  is  to  try  to  develop  a  firm  yet 
gentle  touch.  In  handling  the  lips,  the  cheek,  the  tongue,  the  motions 
should  be  slow  enough  and  deliberate  enough  to  insure  gentleness. 
Such  precautions  in  self-training  soon  improve  the  technic  in  hand- 
ling the  instruments,  and  it  is  much  the  better  fault  to  be  over-gentle 
and  a  little  less  thorough  to  begin  with  than  to  be  heavy-handed, 

5  6  , 

#^      "Is 


Fig.  158 


rough  and  overstrenuous  with  the  instnmients.  There  is  no  better 
application  of  the  golden  rule  than  in  dentistry,  and  the  operator 
who  masters  a  fine  sense  of  touch  and  constantly  keeps  in  mind  a 
sympathetic  consideration  for  his  patient,  has  conquered  much  that 
is  productive  of  success. 

One  of  the  most  perplexing  and  yet  one  of  the  most  essential  things 
to  master  at  the  start  is  the  proper  handling  and  use  of  the  mouth 
mirror.  The  mouth  mirror  is  especially  essential  in  operating  on  the 
lingual  surfaces  of  the  upper  teeth  and  can  also  be  used  to  advantage 
in  holding  the  tongue  away  from  the  lingual  surfaces  of  the  lower 
teeth. 

As  the  motion  reflfected  .in  the  mirror  is  reversed  from  that  of  direct 
observation,  it  is  puzzling  at  first  to  place  the  instrument  properly, 
but  a  little  practice  will  soon  obviate  the  difficulty.    The  Dunn  cheek 


244 


DENTAL  PROPHYLAXIS 


distender  is  used  to  expose  the  buccal  surfaces  of  the  teeth,  both  in 
instrumentation  and  poHshing,  and  its  use  adds  much  to  ease  of  vision 
and  access  to  these  surfaces. 

The  Four  Motions. — In  instrumentation,  as  well  as  in  polishing,  there 
are  four  distinct  motions.  These  may  be  termed  digital,  wrist,  rotary 
or  forearm  and  rigid  arm.  In  acquiring  these  movements  the  fulcrum 
point  of  the  hand  in  relation  to  the  hold  of  the  instrument  is  the  deter- 
mining factor.  If  the  digital  motion  is  to  be  used,  the  instrument 
or  polisher  is  grasped  as  illustrated  in  Fig.  159.  The  end  of  the  right 
thumb  is  the  fulcrum-point  or  rest.  This  position  permits  of  a  perfect 
control  of  the  instrument  and  allows  a  play  of  the  instrument  in 
either  a  push  or  a  pull  stroke.  This  motion  is  used  particularly  on 
the  teeth  of  the  upper  jaw.  It  might  be  well  to  state  here  that  no 
instrument  should  be  used  in  the  mouth  unless  the  hand  is  first  braced 


Fig.  159 


by  a  suitable  rest  for  one  or  more  of  the  fingers  of  the  hand  holding 
the  instrument.  No  free-hand  motion  should  be  used.  Such  motions 
would  be  almost  sure  to  invite  a  slip  of  the  instrument  and  result  in 
laceration  of  the  gum  tissue.  The  wrist  motion  is  acquired  by  holding 
the  instrument  as  illustrated  in  Fig.  160,  using  the  end  of  the  second 
or  third  fingers  as  a  fulcrum.  This  motion  may  be  used  in  various 
parts  of  the  mouth,  especially  on  the  lingual  surfaces  of  the  molars 
and  bicuspids,  but  it  is  not  as  effective  for  general  use  as  the  forearm 
or  rotary  movements.  The  forearm  or  rotary  motion  is  used  on  both 
the  upper  and  lower  jaws  and  usually  the  end  of  the  third  finger 
serves  as  a  fulcrum,  although  that  of  the  second  finger  can  sometimes 
be  used.  This  motion  is  produced  by  holding  the  muscles  quite  rigid, 
permitting  the  radius  to  rotate  around  the  ulna  bone  in  a  limited  area. 
After  a  little  practice  this  motion  permits  of  a  rapidity  of  work  with  the 


THE  PRINCIPLE,^  OP  DENTAL  PROPHYLAXIS 


245 


instrument  under  perfect  control,  and  to  master  this  stroke  is  to  master 
much  of  the  technic  of  instrumentation  and  polishing. 


Fig.  160 

Fig.  161  illustrates  the  position  of  the  hand  when  using  the  rotary 
motion. 


Fig.  161 


The  rigid-arm  motion  is  used  for  polishing  nearly  all  of  the  labial 
and  buccal  surfaces  of  the  teeth,  both  upper  and  lower,  and  for  the 
lingual  surfaces  of  the  molars  and  bicuspids.    The  rest  is  usually  found 


246 


DENTAL  PROPHYLAXIS 


by  using  the  side  of  the  second  joint  of  the  right  thumb  on  the  chin  or 
the  second  joint  of  the  third  or  fourth  finger  as  ihustrated  in  Fig.  162. 

The  muscles  of  the  whole  arm  are  made  fairlj-  tense  and  the  arm  is 
made  to  travel  forward  and  backward  in  a  short,  limited  area.  All 
of  these  motions  should  be  practised  over  and  over  again  on  manikins 
before  being  tried  in  the  mouth.  They  are  not  easy  to  master  and  the 
muscles  must  be  trained  by  repeated  practice. 

In  the  removal  of  tartar  around  the  necks  of  the  teeth,  there  are 
two  strokes  that  may  be  utilized,  a  push  stroke  and  a  pull  stroke. 
Which  to  use  is  determined  in  a  great  measure  upon  the  quantity  or 
bulk  of  the  deposit  and  also  upon  the  tenacity  with  which  it  may  cling 
to  the  tooth  surface.  In  scaling  off  pieces  of  hard  deposits,  large  or 
small,  the  draw  or  pull  stroke  will  be  found  most  effective.  The  instru- 
ment is  carefully  carried  a  little  below  the  gingival  border  of  the  gum 
and  hooked  securely  over  the  shoulder  of  the  deposit.     Then  with  the 


hand  properly  braced,  the  instrument  is  firmly  drawn  toward  the  masti- 
cating surface  or  cutting  edge  of  the  tooth — a  second  digital  motion 
(Fig.  162).  When  the  deposits  are  small  and  fairly  soft,  a  short, 
pushing  stroke  will  be  more  effective. 

Instraments. — Before  the  handling  of  the  instruments  is  described 
in  detail  a  set  of  scalers  will  be  considered  that  should  be  sufficient 
for  the  beginner  for  all  prophylactic  work  upon  the  necks  and  crowns 
of  the  teeth.  These  include  eleven  instruments  and  may  be  described 
as  follows : 

Fig.  163.  The  two  small  curved  instruments  with  the  spoon-like 
ends  are  known  as  Nos  17  and  18  of  the  set  of  Darby-Perry  excava- 
tors. They  are  curved  in  opposite  directions  to  each  other  and  are 
paired  as  rights  and  lefts.  Dr.  C.  W.  Strang,  of  Bridgeport,  Ct., 
suggested  their  use.  Nos.  5  and  6  belong  to  the  D.  D.  Smith  set  and 
are  made  by  J.  W.  Ivory,  of  Philadelphia.    Fig.  164,  Nos.  13  and  14, 


Ta^  PtttNClPLMS  6P  DENTAL  PROPHYLAXIS  ^47 


6  IS 

Fig.  163 


17 


Fio.  164 


248 


DENTAL  PROPHYLAXIS 


were  designed  by  Dr.  E.  S.  Gaylord,  of  New  Haven,  Ct.,  and  are  a 
part  of  the  Smith  set,  and  are  also  made  by  J.  W.  Ivory,  Nos.  3 
and  4  are  from  the  Harlan  set  of  scalers  made  by  the  S.  S.  White 
Company. 

Fig.  165  illustrates  the  S.  S.  White  scalers  Nos.  33  and  34  and  No.  3 
sickle-sha,ped,  which  are  all  used  for  the  removal  of  heavy  deposits  by 
the  pull  or  digital  stroke. 

The  use  of  No.  3  sickle-shaped,  and  Nos.  33  and  34  is  especially 
indicated  in  the  first  treatment  of  mouths  where  the  deposits  have 
accumulated  for  some  time.  For  subsequent  treatments  the  smaller 
instruments  mentioned  should  meet  the  requirements  of  the  dental 


Fig.  165 

hygienist.  At  this  point  it  must  be  distinctly  understood  that  the 
cleaning  of  teeth  bears  the  same  relationship  to  dental  prophylaxis 
as  plowing  does  to  agriculture.  The  plowing  is  essential  before  the 
science  of  agriculture  can  be  applied.  The  removal  of  the  heavy 
deposits,  large  accretions  and  accumulations  of  stains  and  plaques  is 
essential  before  the  real  science  of  prevention  can  be  applied.  A  true 
prophylactic  treatment  must  be  designed  to  aid  in  the  prevention,  not 
only  of  dental  caries,  but  of  any  of  the  departures  from  the  normal 
of  the  supporting  tissues  of  the  teeth.  It  must  constitute,  then,  the 
painstaking,  frequent  and  systematic  removal  from  the  exposed 
surfaces  of  every  tooth  the  granular  deposits,  the  accretions  and 
incipient  plaques  by  instruments  and  hand  polishers. 


INSTRUMENT  A  TION 


249 


INSTRUMENTATION. 

Lower  Jaw. — Assuming  that  the  deposits  are  not  unusual  in  quantity 
and  are  reasonably  easy  to  remove,  the  adaptation  of  these  instru- 
ments will  be  described,  proceeding  as  in  Fig.  l.'jo. 

Starting  at  the  distolingual  angle  of  the  right  lower  last  molar. 
No,  18  of  the  Darby-Perry  excavators  is  selected  and  held  at  the  angle 
shown  in  Fig.  166.  The  stroke  used  is  a  short  downward  push,  and 
a  wrist  motion  is  used  with  the  blade  held  at  nearly  a  right  angle  with 
the  tooth.  On  the  downward  stroke,  the  back  of  the  blade  with  its 
smooth,  blunt  surface  will  strike  the  gingival  border  of  the  gum  and 


Fig.  166 


prevent  the  cutting  edge  of  the  instrument  from  traveling  far  enough 
to  injure  the  subgingival  tissues.  This  short  stroke  is  rapidly  repeated, 
the  operator  making  a  wave-like  motion  of  the  instrument,  gradually 
moving  it  forward,  mesially,  on  the  lingual  surface  of  the  molar  until 
the  mesiolingual  angle  is  turned,  and  using  the  mouth  mirror  with 
the  left  hand  to  keep  the  tongue  out  of  the  way.  The  instrument  is 
now  transferred  to  the  next  molar  and  the  operation  is  repeated.  This 
is  continued  with  the  same  instrument  until  the  left  lower  central  is 
reached,  from  No.  1  to  No.  2  in  Fig.  153.  The  mate  to  this  instrument, 
No.  17,  is  now  substituted  and  the  operator,  starting  on  the  lingual 
surface  of  the  left  central,  Fig.  167,  and  using  a  rotary  stroke,  continues 
until  the  distolingual  angle  of  the  left  lower  last  molar  is  reached, 


250. 


bmfAL  PROPHYLAXIS 


Fig.  168  or  from  No.  3  to  No.  4  in  Fig.  153.  These  small  instruments 
greatly  magnify  the  sense  of  touch,  so  that  each  small  deposit  is  readily 
felt,  whereas  a  larger  instrument  might  pass  it  by. 


Fig.  167 


Fig.  168 


INSTRUMENTA  TION 


251 


Fig.  169 


■ 

l^^jJCX 

^^ 

ft 

K^'IHf^^iJ^I^^^^^^^^^^I 

f 

Fig.  170 


252 


DENTAL  PROPHYLAXIS 


Again  starting  at  the  distobuccal  angle  of  the  left  last  molar  with 
instrument  No.  18,  Fig.  169,  this  short,  pushing  stroke  with  a  wrist 
motion  is  used  until  the  left  lateral  is  reached.  From  No.  5  to  No.  6 
in  Fig.  153.  Although  the  same  instrument  can  be  used  effectively 
on  the  labial  surfaces  of  the  incisors,  it  will  be  found  advantageous 
to  change  for  its  mate,  No.  17,  and,  leaning  slightly  in  front  of  the 
patient,  brace  the  hand  by  the  third  finger  on  the  masticating  surface 
of  the  first  bicuspid  (Fig.  170),  using  a  wrist  motion  which  permits 
of  a  careful  handling  of  the  festoons  of  the  gums  of  the  lower  incisors. 
After  the  labial  surface  of  the  left  lateral  is  finished,  the  hand  is  moved 


Fig.  171 


forward  to  engage  the  next  tooth.  At  the  right  cuspid  the  rotary  stroke 
is  now  adopted  and  continued  to  the  last  molar.  Fig.  171  or  from  No. 
7  to  No.  8  in  Fig.  153.  The  finger  rests  for  the  work  just  described  are 
found  on  the  masticating  surfaces  of  the  bicuspids  or  on  the  cutting 
edge  of  the  cuspid  or  incisors. 

The  base  of  each  tooth  has  four  lines.  Two  of  these  lines  have  now 
been  covered,  and  there  remains  the  approximal  surfaces  or  the  distal 
and  mesial  lines.  No.  13  is  an  instrument  with  the  end  bent  at  an 
angle  of  forty-five  degrees,  having  a  long  blade  with  a  file-cut  surface, 
the  numerous  small  blades  of  which  are  very  effective  in  removing 


INSTRUMENT  A  TION 


253 


the  small  deposits.     This  instrument  should  be  used  chiefly  with 
a  pull  stroke,  starting  at  No.  1,  in  Fig.  154,  which  is  the  distal  sur- 


FiG.  172 


Fig.  173 


face  of  the  right  lower  last  molar,  as  shown  in  Fig.  172.     The  distal 
surface  of  the  last  molar  being  free,  the  blade  is  carefully  passed 


254 


DENTAL  PROPHYLAXIS 


down  under  the  gum  line  until  the  sense  of  touch  determines  the  bot- 
tom of  the  subgingival  space.  The  blade  is  then  brought  tight  against 
the  tooth  surface  and  pulled  upward.  An  eighth  to  a  quarter  of  an 
inch  play  of  the  blade  is  sufficient  to  dislodge  the  deposits.  This  stroke 
is  rapidly  repeated  across  the  back  of  the  tooth.  In  adapting  this 
instrument  to  the  distal  surface  of  the  second  molar  the  blade  is  inserted 
sidewise  from  the  buccal  surface  (Fig.  173),  and  with  a  short  push-and- 
pull  stroke  the  instrument  is  worked  between  the  teeth  in  order  to 
cover  the  entire  distal  line.  If  the  teeth  are  so  shaped  and  are  so 
close  together  that  they  will  not  permit  the  blade  to  pass  between  them, 
then  the  instrument  should  be  inserted  also  from  the  lingual  surface, 
and  in  this  way  that  part  of  the  distal  line  that  was  inaccessible  from 


Fig.  174 


the  buccal  surface  is  covered.  With  the  same  instrument  the  distal  sur- 
faces of  the  teeth  may  be  scaled  to  the  incisors,  or  from  No.  1  to  No.  2, 
in  Fig.  154.  Again,  with  the  same  instrument,  the  operator  should  start 
on  the  distal  surface  of  the  left  cuspid,  and  entering  from  the  buccal 
side,  proceed  on  to  the  last  molar,  or  from  No.  3  to  No.  4,  in  Fig.  154. 
The  procedure  for  the  mesial  surfaces  is  the  same  as  described  for  the 
distal,  except  that  the  instrument  used  is  No.  14,  and  one  position  is 
illustrated  as  in  Fig.  174.  Both  push  and  pull  strokes  are  employed. 
The  lower  incisors  are  scaled  on  their  approximal  surfaces  by  the 
bayonet-shaped  Smith  scalers,  Nos.  5  and  6,  from  No.  5  to  No.  6  of 
Fig.  155,  which  shows  this  area.  Fig.  175  illustrates  the  adaptation  of 
these  instruments. 


INSTRUMENTATION 


255 


Upper  Jaw. — On  the  upper  jaw,  at  the  right  distolingual  angle  of  the 
last  molar,  instrument  No."  17  is  placed  at  nearly  a  right  angle  with  the 
tooth  and,  with  the  hand  braced  on  the  top  of  the  left  lower  lateral 
and  cuspid  teeth,  using  the  third  finger  as  fulcrum  (Fig.  176),  a  wrist 


Fig.  175 

and  digital  motion  is  employed,  the  instrument  being  made  to  travel 
forward  with  a  short  up-and-down,  push-and-pull  stroke  combined, 
perhaps  better  described  as  a  waving  stroke.  The  fulcrum-point  is 
maintained,  the  instrument  being  drawn  in  or  shortened  as  the  inci- 
sors are  approached.  When  the  left  central  is  reached  (Fig.  156), 
instrument  No.  18  is  substituted,  the  second  finger  used  as  a  fulcrum 


Fig.  176 


on  the  cutting  edge  of  the  right  upper  cuspid  (Fig.  177)  and  the  lingual 
surfaces  of  the  upper  teeth  of  the  left  side  are  gone  over  with  a  wrist 
and  digital  motion.  This  fulcrum-point  is  maintained  and  the  instru- 
ment advanced  in  length  with  the  thumb  and  first  finger  (Fig.  178). 


256 


DENTAL  PROPHYLAXIS 


Again  starting  at  the  distobuccal  angle  of  the  left  upper  third  molar, 
the  third  finger  is  placed  slightly  back  of  the  cutting  edge  of  the  right 
upper  lateral  and  central  while  the  second  finger  rests  on  the  cutting 
edge  of  the  left  upper  central  (Fig.  179) .  This  position  can  be  held  until 
the  left  lateral  is  reached,  the  motion  being  wrist  and  digital.  Shifting 
the  fulcrum-point  to  the  end  of  the  third  finger  on  the  edge  of  the  right 
upper  cuspid,  the  labial  surfaces  of  the  left  central  and  lateral  may  be 
scaled  with  the  same  instrument.     With  the  hand  resting  against  the 


Fig.  177 


chin  just  below  the  lower  lip,  and  the  third  joint  of  the  little  finger 
serving  as  a  fulcrum,  with  instrument  No.  18,  the  right  central  and 
from  there  back  to  and  including  the  third  molar  is  scaled,  using  the 
digital  motion,  as  in  Fig.  180. 

The  lingual  as  well  as  the  labial  and  buccal  surfaces,  having  been 
covered,  No.  13  is  used  for  the  distal  surfaces  (Fig.  157)  of  all  the  upper 
teeth  excepting  the  incisors.  For  the  molars,  bicuspids  and  cuspids  of 
the  upper  jaw  the  description  of  the  use  of  this  instrument  for  those 


INSTR  UM  EN  TA  TION 


257 


on  the  lower  jaw  may  be  applied,  the  hand  rest  being  found  chiefly 
on  the  cutting  edge  of  the  lower  incisors,  the  end'  of  the  third  finger 


Fig.  178 


17 


Fig.  179 


258 


DENTAL  PROPHYLAXIS 


serving  for  fulcrum.    No.  14,  Fig.  158,  is  used  in  a  similar  manner  with 
the  hand  rests  the  same  as  for  No.  13.    Nos.  5  and  6  are  best  adapted 


Fig.  180 


Fig.  181 


for  the  approximal  surfaces  of  the  incisors,  their  use  at  this  point  being 
too  self-evident  to  need  explanatiop, 


INSTRUMENTATION  259 

Even  with  this  detailed  description,  much  will  be  found  lacking  to 
the  beginner,  but  after  a  little  practice  on  the  manikin  the  hand  will 
soon  adjust  itself  to  the  proper  rests  to  secure  the  greatest  efficiency 
and  control  of  the  instrument. 

In  removing  the  heavy  deposits  the  sickle-shaped  instrument,  No.  3, 
and  scalers  Nos.  33  and  34  will  be  found  most  useful.  In  skilful  hands 
it  is  possible  to  scale  roughly  nearly  all  the  surfaces  of  all  the  teeth 
with  these  instruments,  the  exception  being  the  approximal  surfaces. 
No.  3  is  used  with  a  draw  or  pull  stroke  and  has  the  advantage  of  not 
being  dangerous  around  the  anterior  teeth,  for  the  point  of  the  instru- 
ment as  well  as  the  side  of  the  blade  is  inserted  under  the  deposit  and 
pulled  directly  upward  on  the  lower  teeth  and  downward  on  the  upper 
teeth.  But  in  the  back  of  the  mouth  where  its  adaptation  necessitates 
the  drawing  of  the  instrument  forward  under  the  border  of  the  gingiva, 
the  point  is  likely  to  slip  and  travel  too  deep  into  the  subgingival  space 
unless  care  is  used.  A  firm  hold  on  the  instrument  and  a  secure  brace 
of  the  hand  is  absolutely  essential.  This  sickle-shaped  instrument 
is  used  almost  entirely  with  a  digital  motion  and  the  two  principal 
positions  are  illustrated  in  Figs.  182  and  183.  It  is  very  difficult  to 
scale  the  teeth  thoroughly  with  this  instrument,  but  the  larger  deposits 
having  been  removed  at  the  first  sitting,  Nos.  17  and  18  can  be  used  to 
advantage  at  the  second  and  all  subsequent  treatments. 

The  Harlan  instruments,  Nos.  3  and  4,  are  also  used  with  a  draw 
stroke  and  are  helpful  in  removing  th6  small,  hard,  tenacious  deposits 
under  the  free  margin  of  the  gums.  They  are  adaptable  in  nearly  all 
sections  of  the  mouth  and  their  use  is  usually  self-suggestive.  When 
these  small  deposits  resist  Nos.  17  and  18,  especially  on  the  bicuspids, 
cuspids  and  incisors,  these  Harlan  instruments  will  be  found  very 
effective. 

If  uncertainty  exists  in  the  mind  regarding  the  thorough  removal 
of  all  deposits,  an  instrument  known  as  an  explorer  carefully  passed 
around  the  neck  of  the  tooth  under  the  gingivae  will  readily  detect 
any  small  deposits  or  uneven  surfaces.  The  smaller  the  instrument, 
the  more  greatly  is  the  sense  of  touch  magnified.  It  is  for  this  reason 
that  the  use  of  Nos.  17  and  18  is  advised  wherever  practical. 

There  are  two  special  features  to  be  considered  under  instrumenta- 
tion :  First,  the  sensitiveness  that  is  frequently  found  around  the  necks 
of  the  teeth,  and  second,  the  bleeding  of  the  gingival  borders  of  the 
gums.  In  adults  where  the  lime  deposits  have  been  heavy,  their  re- 
moval will  frequently  cause  much  sensitiveness  for  a  week  or  two, 
sometimes  even  longer,  to  heat  and  cold  and  to  sweets  and  acids.  The 
deposits  have  caused  an  absorption  of  the  border  of  the  alveolar  process, 
the  soft  tissues  and  the  cementum  around  the  necks  of  the  teeth,  and 
when  they  are  removed  the  interglobular  spaces  on  the  border  between 
the  dentin  and  the  cementum  are  exposed,  presenting  an  area  that  is 
highly  sensitive  to  the  touch  of  the  instrument  or  polisher.  It. is  fre- 
(^uently  wise  to  inform  the  patient  that  he  maj^  expect  the  surfaces  to 


260 


DENTAL  PROPHYLAXIS 


Fig.  182 


Fig.  183 


POLISHING  261 

be  responsive  to  heat  and  cold  for  a  short  time,  in  order  to  allay  any 
fears  on  his  part.  The  deposits  acting  as  a  covering  for  these  surfaces 
have  protected  them  from  external  irritation,  and  the  patients  are  apt 
to  wonder  why  it  is  that  their  mouths  are  so  much  more  sensitive  than 
they  were  before  the  deposits  were  removed.  Acids  are  especially 
irritating  to  these  surfaces  and  the  use  of  bicarbonate  of  soda,  half  a 
teaspoonful  to  a  third  of  a  glass  of  warm  water,  used  as  a  mouth  wash 
two  or  three  times  daily,  will  aid  greatly  in  tiding  over  this  short  period 
of  discomfort.  If  the  soda  can  be  used  clear  by  dipping  the  finger  in 
water,  touching  it  to  the  soda  and  then  rubbing  it  on  these  surfaces,  it 
will  all  the  more  quickly  neutralize  any  acid  that  may  be  irritating 
to  this  sensitive  tissue.  The  thorough  rubbing  and  polishing  with 
the  stick  and  pumice  and  the  extreme  cleanliness  from  the  faithful 
use  of  the  tooth-brush  will  soon  bring  these  troublesome  areas  under 
control.  The  application  of  a  10  per  cent,  solution  of  nitrate  of  silver  is 
sometimes  advised,  but  if  it  is  used,  it  should  be  followed  by  a  thorough 
polishing  with  the  stick  and  pumice. 

The  second  feature,  which  will  be  considered  briefly,  is  the  bleed- 
ing of  the  gums  during  instrumentation.  When  the  gums  readily 
bleed  there  is  congestion  of  the  capillaries,  and  the  more  blood  allowed 
to  escape  from  the  gingivae,  the  sooner  the  congestion  will  be  relieved. 
Instead  of  trying  not  to  make  the  gums  bleed,  just  the  reverse  course 
should  be  followed,  although  of  course  this  does  not  mean  that  they 
should  be  lacerated  or  the  tissue  wounded.  The  bleeding  process  is 
produced  by  using  the  back  or  smooth  surface  of  the  blade  of  the  instru- 
ment with  pressure,  and  this  is  done  while  removing  the  lime  deposits, 
and  if  there  is  a  copious  flow  of  blood  from  some  of  the  approximal 
surfaces,  it  should  be  encouraged  by  rapid,  gentle  pressure  strokes 
directly  on  the  gingivae.  Healthy  gums  will  not  bleed  during  instru- 
mentation, and  when  bleeding  occurs  enlarged  and  congested  capilla- 
ries are  sure  to  be  found.  No  fear  of  causing  injury  to  the  gum  tissue 
in  causing  a  flow  of  blood  need  be  felt  as  long  as  care  is  taken  that 
the  blade  of  the  instrument  does  not  cut  the  tissue.  Frequently  after 
such  a  treatment  the  gums  will  take  on  a  color  two  shades  lighter  before 
the  patient  leaves  the  chair,  and  after  a  few  days  of  stimulation  with 
the  tooth-brush  it  will  be  hard  to  recognize  it  as  the  deep  red,  congested 
tissue  that  it  was  at  first. 

POLISHING. 

It  is  impossible  to  obtain  the  same  results  in  prophylaxis  with  the 
use  of  the  dental  engine  in  polishing  as  may  be  secured  with  the  hand 
polishers.  This  belief  is  based  upon  personal  experience  in  faithfully 
trying  out  both  methods,  and  is  an  accepted  fact  by  all  prophylactic 
workers  who  have  become  proficient  with  the  hand  polishers. 

The  object  of  this  polishing  process  is  threefold :  First,  the  removal 
of  stains,  plaques  and  films  or  all  soft  accretions  on  the  exposed  sur- 
faces of  the  teeth.     Second,  a  polishing  of  the  enamel  surfaces  and  a 


262 


DENTAL  PROPHYLAXIS 


stimulating  effect  that  seems  to  be  imparted  to  the  living  tissue  of 
the  tooth  itself  by  the  vigorous  massage.  Third,  the  beneficial  results 
obtained  on  the  gingival  borders  of  the  gums  by  the  slight  bumping 
of  the  stick,  causing  light  pressure  and  release  which  imparts  a  massage 
effect  and  aids  greatly  in  producing  a  perfect  flow  of  blood  through 
the  capillaries  in  the  peripheral  circulation.  If  a  new  case  presents 
itself  in  which  the  teeth  are  very  badly  stained,  it  is  perfectly  reason- 
able, if  desired,  to  use  the  dental  engine  for  the  first  treatment  to  aid 
in  cleaning  off  these  stains  from  the  enamel  surfaces,  but  all  subsequent 
treatments  should  be  made  with  the  hand  polishers.  An  engine 
revolving  at  six  or  eight  hundred  revolutions  a  minute,  with  the  rubber 
cup  or  buff  charged  with  pumice,  cuts  too  viciously  and  if  used  at  each 


Fig.  184 


prophylactic  treatment,  will  in  time  affect  the  enamel  and  tooth  struc- 
ture at  the  necks  of  the  teeth.  With  the  dental  engine  all  sense  of  touch 
is  lost,  and  besides  it  is  not  as  adaptable  on  the  approximal  surfaces 
or  on  the  surfaces  of  the  molars  as  the  stick  held  in  the  hand.  The 
gingival  borders  of  the  gums,  in  many  mouths,  have  been  badly 
wounded  or  damaged  by  the  revolving  cups  or  buffs  in  the  dental 
engine,  and  if  one  hopes  and  expects  to  secure  the  best  results  in  obtain- 
ing ideal  health  conditions  of  these  tissues,  one  must  become  proficient 
with  the  hand  polishers.  Those  who  would  advocate  the  dental  engine 
are  those  who  have  failed  to  make  themselves  proficient  with  the  hand 
polishers.  There  can  be  no  choice  if  the  latter  is  faithfully  tried. 
There  are  a  number  of  different  woods  that  may  be  used  for  polishing, 
as  cedar,  maple,  hard  pine,  etc.,  but  the  closest-grained  wood  and  the 


POLISHING 


263 


one  best  adapted  for  this  purpose  is  oranj^e  wood.  Tliere  are  two  sizes 
of  sticks  that  may  be  had  from  the  dental  depots,  known  as  large  and 
small.  The  large  size  is  cut  about  three  quarters  of  an  inch  in  length 
and  one  end  is  trimmed  wedge-shaped.  This  stick  is  used  on  all  the 
broad  surfaces  of  the  teeth  excepting  the  masticating  surfaces.  The 
small  stick  is  cut  about  the  same  length  and  one  end  is  sharpened  like 
the  point  of  a  lead-pencil.  The  smaller  stick  is  used  on  the  approximal 
surfaces  and  around  the  necks  of  the  teeth  where  it  is  impossible  to 
adapt  the  larger  stick.  In  order  to  work  with  facility,  two  holders 
for  the  two  sizes  of  sticks  should  be  employed.  Fig.  184  illustrates  the 
Jack  porte  polishers  with  sticks  in  position. 

As  a  slight  abrasive  and  polish  to  be  used  with  the  sticks,  the  finest 
grade  of  pumice  moistened  with  water  will  prove  to  be  the  most  satisfac- 
tory. x\lthough  other  polishing  mediums  are  used  with  good  results,  it 
is  doubtful  if  there  is  anything  superior  to  fine  pumice  for  this  special 


Fig.  185 


work.  A  scant  spoonful  placed  in  a  small  porcelain  dish,  and  wet 
sufficiently  with  water  to  be  almost  liquid,  will  make  a  mixture  that 
can  readily  be  picked  up  on  the  point  of  the  wet  stick  and  used  in  the 
mouth. 

System  for  Polishing. — Just  as  a  definite  system  is  employed  in  going 
over  the  teeth  with  the  instruments,  so  should  a  system  for  reaching 
all  surfaces  of  the  teeth  with  the  polishers  be  followed. 

The  following  system  is  very  effective  and  its  adoption  is  suggested, 
at  least  for  beginners : 

Starting  on  the  labial  surface  of  the  right  upper  central  with  the 
large  stick,  the  polishing  progresses  to  the  right  lateral,  then  to  the 
right  cuspid  and  so  on  until  the  right  last  molar  is  reached.  From 
this  point  start  on  the  buccal  surface  of  the  right  lower  last  molar 
and  progress  forward  around  the  buccal  and  labial  surfaces  of  all  the 
lower  teeth  to  the  left  lower  last  molar.     Transferring  the  stick  to  the 


264 


DENTAL  PROPHYLAXIS 


buccal  surface  of  the  left  upper  last  molar,  the  polishing  is  continued 
forward  to  the  median  line  to  and  including  the  left  upper  central. 
All  the  labial  and  buccal  surfaces  have  now  been  polished  with  the  use  of 
only  the  larger  stick.  Fig.  185  illustrates  direction  for  polishing.  Then 
starting  on  the  lingual  surface  of  the  right  lower  last  molar  with  the 
large  stick,  the  polishing  of  the  lingual  surfaces  proceeds  forward  to 
the  incisors,  then  backward,  or  distally,  to  the  lingual  surface  of  the 
left  lower  last  molar.  Again  beginning  on  the  lingual  surface  of  the 
left  upper  last  molar,  all  of  the  lingual  surfaces  are  covered,  ending  on 
the  right  upper  last  molar. 

So  far  only  the  large  stick  has  been  used.  Now  with  the  pointed 
stick  the  same  course  should  be  followed  over  the  teeth  as  has  just 
been  described,  polishing  in  between  the  teeth  as  far  as  possible  and 


Fig.  186 


rubbing  the  necks  of  the  teeth  under  the  free  border  of  the  gingivae, 
keeping  the  edge  of  the  stick  sharp.  When  they  become  frayed  or 
brush-like,  they  should  be  trimmed  off  with  a  pair  of  scissors,  or  if, 
after  this,  the  edges  are  still  too  blunt,  sharpened  with  a  knife. 

The  polishing  is  confined  almost  entirely  to  two  motions,  the  rigid- 
arm  and  the  forearm  or  rotary.  The  one  exception  is  the  digital  that 
should  be  used  by  beginners  on  the  labial  surfaces  of  the  upper  incisors. 

In  order  to  polish  effectively  pressure  must  be  used.  It  is  this  one 
point  of  being  able  to  apply  pressure  on  all  the  surfaces  while  polish- 
ing that  makes  the  operation  difficult.  This  is  noted  especially  in 
polishing  the  lingual  surfaces  of  the  molars  and  bicuspids.  The  proper 
hand  rests  are  essential  and  also  muscular  practice  of  the  motions 
used  for  this  work. 

Beginning  on  the  labial  surface  of  the  right  upper  central  with  the 


POLISHING 


2Go 


large  stick,  and  using  a  digital  motion,  the  stick  is  made  to  travel  up 
and  down  the  full  length. of  the  face  of  the  tooth,  rubbing  the  surface 
with  both  up  and  down  strokes.     The  stick  is  allowed  to  bump  the 


Fig.  187 


Fig.  188 


gum  lightly  but  not  hard  enough  to  cause  discomfort.  Considerable 
pressure  is  used  and  the  motion  is  rapid.  Fig.  186  illustrates  the  posi- 
tion of  the  hand  with  the  thumb  rest  on  the  cuspid  for  the  digital 


m 


MNfAL  PROPHYLAXIS 


motion.  When  the  right  cuspid  is  reached  the  rigid-arm  motion  is 
employed,  with  the  back  of  the  second  finger,  between  the  second  and 
third  joints,  resting  on  the  side  of  the  chin  and  the  two  bicuspids  are 
rubbed  and  poUshed  up  and  down  or  longitudinally,  the  right  thumb 
pressing  on  the  polisher  at  the  end  of  the  stick  (Fig.  187) .  Now  insert- 
ing the  Dunn  cheek  distender,  the  buccal  surfaces  of  the  molars  are 
rubbed  crosswise,  using  the  rotary  motion  and  the  same  fulcrum  posi- 
tion that  was  used  with  the  cuspid  and  bicuspid,  but  the  porte  polisher 
is  shifted  in  the  hand  and  grasped  as  one  would  hold  a  pen-holder 
(Fig.  188).  The  end  of  the  stick  may  be  made  to  travel  up  and 
down  part  way  on  the  approximal  surfaces,  but  the  principal  motion 
for  polishing  is  crosswise.  The  polishing  of  the  right  lower  molars 
is  the  same  as  described  for  the  upper  molars.     For  the  right  lower 


Fig. 189 


cuspids  and  bicuspids,  the  same  as  for  the  upper.  The  first  finger 
of  the  left  hand  now  is  placed  across  the  inside  of  the  lip  to  depress 
it  and  with  the  polisher  grasped  in  the  fist  with  right  thumb  resting 
on  the  left  forefinger  (Fig.  189),  the  lower  incisors  are  polished.  For 
the  left  cuspid  and  bicuspids  the  same  position  as  for  the  right  is  used. 
In  polishing  the  left  lower  and  upper  molars  the  back  of  the  third  finger 
becomes  the  fulcrum  on  the  side  of  the  chin  and  the  polisher  is  grasped 
pen-holder  fashion,  as  in  Fig.  190,  using  the  rigid-arm  motion.  The 
descriptions  of  the  right  cuspid  and  bicuspids,  lateral  and  central,  will 
apply  to  the  left.  It  will  be  noted  that,  with  the  exception  of  the 
upper  incisors  and  right  molars,  the  motion  used  on  all  the  outer  sur- 
faces of  the  teeth  has  been  rigid-arm.  That  on  the  inner  surfaces  of 
both  lower  and  upper  is  forearm  or  rotary.    The  difficulty  met  with  is 


POLTSftTNa 


267 


Fig.  190 


Fig,  191 


268 


DENTAL  PROPHYLAXIS 


that  of  producing  pressure  and  at  the  same  time  retaining  control  and 
length  of  stroke.  With  the  mouth  mirror  in  the  left  hand  to  hold  the 
tongue  away,  the  backs  of  the  third  and  fourth  fingers  are  pressed  against 


Fig.  193 


POLISHING 


269 


the  chin,  and  the  polisher  held  as  the  pen-holder  in  a  rigid  grasp  (Fig. 
191),  the  stick  is  made  to  travel  up  and  down  on  the  inner  surface  of 


Fig.  194 


Fig.  195 


270 


DENTAL  PROPHYLAXIS 


the  right  lower  molars,  the  edge  of  the  stick  pointing  up  and  down  with 
the  long  axis  of  the  tooth.  This  polishing  motion,  it  will  be  noted, 
is  just  the  reverse  from  that  used  on  the  buccal  surfaces.     By  shorten- 


FiG.  196 


Fig.  197 


ing  the  hold  on  the  polisher  the  same  position  is  used  for  polishing 
the  bicuspids  and  cuspids. 

Other  adaptations  of  the  stick  will  be  found  that  are  advantageous 
for  these  surfaces,  such  as  using  the  side  of  the  stick  with  an  up-and- 
^oyoi  stroke  instead  of  its  sharpened  end, 


POLISHING 


271 


By  leaning  forward  in  front  of  the  patient  the  second  finger  is  placed 
on  the  top  of  the  left  cuspid  or  bicuspid  and  with  a  rocking  or  rotary 
motion  of  the  arm  and  stick  the  lower  incisors  are  polished  (Fig.  192). 
The  left  lower  molars  are  polished  with  the  same  pen-holder  grasp,  using 
the  second  finger  as  a  fulcrum  on  the  right  lower  cuspid  or  lateral 
(Fig.  193).  The  mouth  mirror  can  be  used  to  good  advantage  while 
polishing  the  lingual  surfaces  by  having  the  patient  low  enough. 
Starting  on  the  lingual  surface  of  the  left  upper  last  molar,  the  porte 
polisher  is  held  like  the  pen-holder  and,  with  the  end  of  the  third 
finger  resting  on  the  labial  surface  of  the  right  lower  cuspid  (Fig.  194), 
the  molars  are  rubbed  chiefly  up  and  down  with  the  edge  of  the  stick. 
Holding  the  same  fulcrum-point,  the  grasp  on  the  polisher  is  gradually 
shortened  and  the  incisors  are  polished  as  shown  in  Fig.  195.     The 


Fig.  K 


lingual  surfaces  of  the  right  cuspid,  bicuspids  and  molars  are  polished 
with  the  same  hold  of  the  polisher,  the  rest  being  found  on  the  chin, 
using  the  back  of  the  second  joint  of  the  third  finger  (Fig.  196).  The 
motion  used  is  mostly  forearm  or  rotary. 

All  of  the  positions  and  fulcrum-points  described  for  the  large  stick 
apply  also  to  the  small  stick. 

Where  the  gums  between  the  teeth  are  congested,  the  side  of  the  stick 
is  pressed  against  them  with  a  fast,  quick  stroke  to  encourage  the 
bleeding.  Care  should  be  taken  in  the  use  of  both  sticks  not  to  abrade 
the  gingivae,  but  the  light  pressure  with  the  side  of  the  stick  against 
the  gum  margin  will  prove  very  beneficial  (Fig.  197) .  When  sensitive 
surfaces  are  found  at  the  necks  of  the  teeth,  the  pointed  stick  freely 
ch9,rged  with  pumice  is  applied  with  vigor  and  considerable  pressure, 


272 


DENTAL  PROPHYLAXIS 


A  thorough  polishing  of  their  surfaces  will  greatly  aid  in  reducing  the 
sensitiveness. 

Floss  Polishing. — After  polishing  with  the  sticks  there  still  remain 
the  contact  points  and  an  area  on  the  approximal  surfaces  that  have 
not  been  reached.  By  doubling  a  length  of  ligating  silk,  twisting  it 
and  dipping  it  in  water  and  then  in  pumice,  these  surfaces  may  be 
polished  quite  effectually.  When  the  teeth  are  very  close  together  a 
single  strand  will  be  found  sufficient,  as  this  silk  is  larger  in  size  than 
that  sold  for  every-day  flossing.  Cutters'  wide  floss  may  also  be  used 
to  advantage  where  the  space  will  permit.  When  using  the  floss  for 
polishing  it  should  be  passed  between  the  contact  points  with  care, 
so  that  it  will  not  snap  on  the  gum,  drawn  back  and  forth  on  the  distal 


Fig.  199 


surface  of  the  tooth  and  then  pressed  backward  rubbing  the  mesial, 
surface  of  the  adjoining  tooth.  Most  of  the  decay  takes  place  in  these 
surfaces  and  they  must  be  given  careful  attention.  If  the  ends  of  the 
floss  are  wound  around  the  first  fingers  as  illustrated  in  Figs.  198  and 
199,  it  can  be  easily  manipulated. 

Brush  Wheel. — ^The  masticating  surfaces  are  so  uneven  that  a  stick 
cannot  be  used  on  them  very  well,  so  it  will  be  necessary  to  use  a  brush 
wheel  in  the  engine  to  reach  down  in  the  sulci  to  polish  these  surfaces. 
With  the  wheel  dipped  in  water  and  the  edge  of  it  touched  to  wet 
pumice,  the  engine  should  be  run  at  a  moderate  speed  and  the  edge 
of  the  wheel  applied  down  in  the  sulci  of  the  molars  and  bicuspids. 
The  Dunn  cheek-distender  should  always  be  used.     It  is  almost  unnec- 


POLISHING 


273 


essary  to  state  that  the  sticks,  the  pumice,  the  floss  and  the  brush 
wheel  should  not  be  used  a  second  time.  Figs.  200  and  201  show  the 
adaptation  of  this  wheel. 


Fig.  200 


Fig.  201 


Children. — In  the  prophylactic  treatment  of  children  it  is  seldom 
necessary  to  use  the  instruments.  As  it  is  the  roots  of  the  teeth  that 
are  most  susceptible  to  disease  in  adults,  so  are  the  masticating  and 
approximal  surfaces  most  susceptible  in  children.  These  surfaces  should 
be  carefully  polished  with  the  floss  and  pumice,  and  the  sulci  in  the 
masticating  surfaces  with  the  brush  wheel  in  the  engine.  The  polish- 
ing of  all  the  surfaces  of  the  teeth  with  the  sticks  should  be  done  as 
described  for  the  adult. 
18 


274  DENTAL  PROPHYLAXIS 

To  assist  in  the  removal  of  bacterial  plaques  and  green  stains  on  the 
surfaces  of  the  teeth,  a  small  napkin  should  be  used  to  dry  the  teeth, 
then  with  a  pledget  of  cotton  Churchill's  Compound  Tincture  of  lodin 
is  applied  and  allowed  to  dry.  The  iodin  assists  chemically  in  the 
removal  of  plaques  and  stains.  The  thoroughness  of  the  polishing 
operation  may  be  tested  by  applying  iodin  to  all  the  surfaces  of  the 
teeth  after  the  hygienist  considers  the  operation  finished.  The  mouth 
is  then  rinsed  with  warm  water  and  if  the  iodin  has  not  adhered  to 
any  surface  of  the  teeth,  it  may  be  assumed  that  the  plaques  have 
been  thoroughly  removed. 

Attention  is  called  to  a  preventive  treatment  of  the  fissures  in  the 
first  permanent  molars  of  children  that  comes  within  the  province  of 
the  dental  hygienist. 

When  these  fissures  are  found  to  be  exceptionally  deep,  likely  to 
retain  food  debris  and  thus  susceptible  to  decay,  a  quick-setting, 
hydraulic  cement  should  be  mixed,  and  with  cotton  rolls  on  each  side 
of  the  tooth,  the  fissures  should  be  dried  with  warm  air,  and  washed 
with  a  pledget  of  cotton  soaked  with  alcohol,  again  dried  and  then 
with  an  explorer  the  soft  cement  worked  down  into  the  fissures.  As 
the  cement  begins  to  toughen  and  set,  the  end  of  the  second  finger  is 
dipped  in  a  glass  of  water  and  with  the  ball  of  the  finger  the  cement  is 
pressed  firmly  down  into  the  fissures  and  held  there  for  a  moment  or 
two  until  it  has  become  fairly  hard.  The  surplus  can  easily  be  trimmed 
away  and  the  cement  in  the  fisswes  will  last  for  some  time,  acting  as 
a  protection  to  their  surfaces.  It  takes  but  a  short  time  to  renew  it 
when  it  wears  away,  and  will  frequently  save  these  teeth  from  decay 
at  the  susceptible  period  of  from  six  to  twelve  years  of  age. 

Instructions  for  the  Home  Care  of  the  Mouth. — Brushing. — A 
remarkable  condition  of  health  and  beauty  of  the  gums,  and  a  high 
resistance  and  increased  vitality  of  the  pericementum  may  be  developed 
by  the  proper  form  of  brushing.  It  may  be  well  to  first  consider  the 
blood  supply  to  the  pericementum  in  relation  to  the  circulation  in  the 
gum  tissue  itself.  The  blood  supply  to  the  pericementum  may  be 
described  as  follows;  the  small  arteries  entering  the  apical  space  break 
up  into  branches,  one  or  more  of  them  enter  the  pulp  canal  through  the 
apex  of  the  root  and  the  others  pass  down  through  the  fibers  of  the 
pericementum.  During  their  course  through  this  tissue  on  their  way 
to  the  alveolar  border  and  the  gums,  they  both  give  off  and  receive 
branches  through  the  alveolus  and  connect  with  the  plexus  of  small 
bloodvessels  and  capillaries  of  the  gmn  tissue.  It  will  thus  be  apparent 
that  the  blood  circulation  in  the  gums  is  very  intimately  associated 
with  the  circulation  of  the  pericementum.  It  frequently  happens  that 
when  an  alveolar  abscess  develops  at  the  apex  of  the  root  of  a  tooth, 
the  bloodvessels  in  the  apical  space  are  destroyed  yet  the  pericementum 
does  not  suffer  from  lack  of  blood,  for  the  branches  coming  to  it  from 
the  walls  of  the  alveolus  soon  enlarge  and  produce  a  sufficient  supply. 
It  must,  therefore,  be  noted  that  in  order  to  stimulate  the  blood  supply 


POLISHING  275 

of  the  pericementum  it  is  merely  necessary  to  stimulate  the  circulation 
in  the  gum  tissue. 

Fibers  of  the  pericementum  radiate  into  the  gum  tissue  and  strong 
bands  of  fibers  which  form  the  dental  ligament  blend  into  the  periosteum 
of  the  alveolar  process.  Some  of  these  fibers  are  so  close  to  the  surface 
in  the  gum  tissue  that  it  is  not  difficult  to  understand  why  an  unusual 
response  to  health  may  be  obtained  by  surface  stimulation. 

In  the  process  of  masticating  coarse  foods,  a  natural  massage  takes 
place  in  the  following  manner:  The  coarse  foods  sliding  over  the 
surfaces  of  the  teeth  press  upward  on  the  upper  gums  and  downward 
on  the  lower  gums  creating  a  pressure  and  release  on  the  bloodvessels 
in  the  gum  tissue  which  stimulates  the  circulation. 

The  teeth  being  occluded  with  considerable  force  are  pressed  down  in 
their  sockets.  The  pericementum  is  thus  compressed  and  the  blood  is 
squeezed  out  of  the  small  bloodvessels  through  the  walls  of  the  alveolus. 
As  the  jaws  open  and  release  the  pressure  on  the  teeth,  the  pressure 
upon  the  small  bloodvessels  is  also  released  and  the  blood  comes  rushing 
in  again.  This  pressure  and  release  is  similar  in  its  action  to  a  massage 
of  the  tissues  on  the  surface  of  the  body.  Such  a  process  always 
produces  a  free  flow  of  blood,  and  prevents  congestion  or  stasis  in  the 
capillary  circulation. 

Keratin. — In  the  basement  layer  of  the  skin,  cells  are  constantly 
being  formed  and  forced  slowly  upward  toward  the  surface  of  the  body. 
During  their  transit  the  cells  slowK'  change  their  shape,  becoming  long 
and  flat  in  appearance  and  finally  form  the  pavement  or  squamous 
type  of  epithelium  on  the  surface  of  the  skin.  During  this  period,  from 
the  time  of  formation  to  their  arrival  on  the  surface  of  the  body,  a 
gradual  metamorphosis  or  change  takes  place  in  the  protoplasm  of  the 
cell.  The  content  of  the  cell  gradually  begins  to  toughen  and  this 
process  continues  just  in  proportion  to  the  needs  of  protection  against 
undue  friction  or  exposure.  The  horny  hands  of  the  day  laborer,  or 
the  corns  that  form  on  the  feet,  are  examples  of  the  extreme  expression 
of  the  activity  and  change  in  these  cells.  The  content  of  the  cells 
when  so  changed  or  toughened  is  known  as  keratin. 

The  mucous  membrane  of  the  mouth  is  but  a  continuation  or  an 
infolding  of  the  skin.  Its  epithelium  is  of  the  squamous  type  similar 
to  that  of  the  skin,  but  the  stratified  cells  which  have  the  power  of 
forming  keratin  are  found  only  on  those  portions  of  the  mucous  mem- 
brane covering  the  gum  tissue  and  the  roof  of  the  mouth.  If  the  gum 
tissue  is  artificially  stimulated  three  or  four  times  a  day  with  the  bristles 
of  the  tooth-brush,  a  noticeable  change  takes  place  in  the  texture  of  the 
mucous  membrane.  It  soon  loses  that  smooth,  glassy  or  sleazy  appear- 
ance and  under  a  magnifying  glass  shows  a  thickened  or  toughened 
surface  which  seems  to  act  as  a  protective  armor  for  the  underlying 
tissues  and  makes  the  ingress  of  infection  through  the  gum  tissue,  or 
at  the  gingivae,  extremely  difficult.  Inference  should  not  be  made 
that  there  is  produced  a  hornified  mucous  membrane,  except  in  a 


276  DENTAL  PROPHYLAXIS 

modified  sense,  but  a  beneficial  change  takes  place  that  is  much  to  be 
desired.  A  similar  texture  of  membrane  may  be  found  in  the  mouths 
of  carnivorous  animals. 

The  Gums. — In  considering  the  health  of  these  dental  tissues  the 
gums  found  in  the  average  mouth  should  first  be  noted.  Aside  from 
the  unsanitary  aspect  of  the  crowns  of  the  teeth,  the  gums  will  be 
found  to  be  of  a  deep  red  color,  the  gingivae  usually  showing  even  a 
deeper  red.  The  blood  is  almost  stagnant  on  some  of  the  margins, 
and  the  tissues  will  bleed  upon  the  slightest  touch.  Waste  products 
are  not  being  properly  eliminated,  oxidation  is  imperfect  and  blood 
serum,  which  contains  the  lime  salts  for  serumal  deposits,  oozes  in 
the  subgingival  spaces  and  forms  an  ideal  medium  for  bacteria.  These 
are  the  average  gums  of  adults,  who  eat  food  which  requires  but  little 
mastication  and  produces  but  little  friction  on  the  gums,  and  who 
take  scant  care  of  their  mouths.  But  how  quickly  all  of  these  con- 
ditions will  change  under  artificial  stimulation.  The  instant  the  gums 
are  brushed  properly,  the  blood  starts  to  flow  more  rapidly  and  a  new 
life  and  color  make  their  appearance.  After  a  thorough  prophylactic 
treatment  and  a  lesson  in  gum  brushing  it  is  not  unusual  to  see  the 
tissues  lighten  in  color,  possibly  two  or  three  shades  in  twenty-four 
hours.  At  the  end  of  a  week  or  ten  days  they  assume  a  still  lighter 
shade  and  after  periods  ranging  from  three  to  six  months  they  become 
a  light  coral  pink,  and  hold  this  color  as  long  as  they  are  daily  brushed 
and  stimulated.  "^ 

There  is  apparently  a  peculiar  pink  shade  that  practically  every 
individual  may  acquire  if  the  brushing  is  faithfully  followed.  In  fact 
this  color  may  be  taken  for  so  sure  an  index,  that  it  is  easy  to  tell  at  a 
glance  whether  the  patient  has  been  brushing  the  teeth  and  gums  four 
times  daily.  Virtue,  in  this  case,  has  its  own  reward,  for  the  color 
is  always  obtained  when  the  brush  has  been  used  according  to  rule. 
The  gums  should  be  of  uniform  color  in  all  parts  of  the  mouth,  the 
gingivae  showing  no  difference  in  shade  from  that  of  the  body  of  the 
gum. 

Tissue  Stimulation. — If  the  following  rules  are  honestly  observed  the 
same  results  are  assured  in  every  mouth : 

1.  The  form  of  brushing  as  described  in  this  chapter. 

2.  Brushing  long  enough — not  less  than  two  minutes  after  meals. 

3.  Brushing  four  times  a  day. 

Many  cases  have  been  baffling  because  they  would  not  respond  to 
treatment,  but  when  the  patient  gives  a  demonstration  at  the  wash 
bowl,  it  will  show  that  he  makes  some  omissions  or  uses  an  incor- 
rect form  of  brushing  which,  when  corrected,  will  bring  results  in  a 
short  time.  Sometimes  patients  will  claim  to  have  followed  the  rules 
when,  upon  close  investigation,  it  will  be  found  that  they  have  not 
done  so. 

When  the  gum  tissue  will  not  assume  this  light  pink  shade  in  a  few 
months'  time,  and  when  the  patient  is  expert  with  the  tooth-brush  and 


POLiSHlNG  277 

claims  to  follow  the  rules  faithfully,  it  may  be  suspected  that  in  some 
way  the  rules  are  not  lived  up  to  or  that  otherwise  a  very  rare  excep- 
tion has  been  found. 

Evidently  this  color  that  the  gums  assume  under  the  daily  brushing 
is  due  to  the  fast  flow  of  blood  through  the  capillaries,  the  perfect 
oxidation  of  the  cells  and  thorough  removal  of  their  waste  products, 
as  well  as  a  thickening  or  toughening  of  the  epithelial  layer  of  cells  on 
the  surface.  The  festoons  become  pink  and  tough,  the  surface  of  the 
mucous  membrane  loses  its  thin,  glassy  appearance,  and  when  dried 
looks  tough  and  firm.  Also  when  the  edges  of  the  gum  are  dried  they 
do  not  weep.  Little  or  no  serum  oozes  now  from  this  tissue  and  it 
will  be  noted  that  the  serumal  deposits,  found  so  plentifully  under  the 
congested  borders  of  the  gums,  almost  entirely  disappear  at  subsequent 
treatments.  It  must  not  be  assumed  that  the  miraculous  happens 
under  these  unusual  health  conditions  or  that  merely  learning  how  to 
brush  the  gums  will  eliminate  all  present  and  future  disease  of  the 
mouth.  However,  one  cannot  help  being  enthusiastic  when  viewing 
the  rapid  return  to  health  of  the  dental  tissues  under  artificial  stimula- 
tion. The  pericementum  seems  to  acquire  new  life,  and  apparently 
feels  the  stimulation  in  every  fiber  and  cell.  Loose  and  sore  teeth 
become  tight  and  free  from  soreness,  providing  that  too  much  of 
their  supporting  tissue  has  not  been  lost.  Chronic  cases  of  perice- 
mentitis disappear  and  even  the  pi^up  itself  maj'  be  relieved  of  conges- 
tion if  it  is  slight  and  has  not  progressed  too  far.  There  is  no  doubt 
that  the  osteoblasts,  under  prophylaxis  and  this  stimulation,  do  at 
times  replace  small  areas  of  lost  alveolar  process.  Where  roots  have 
been  exposed  on  the  labial  or  approximal  surfaces,  especially  those  of 
the  incisors  and  cuspids,  it  is  not  uncommon  to  see  gum  tissue  creep 
back  over  the  exposed  root  to  a  considerable  degree  and  oti  approximal 
surfaces  there  has  been  a  filling  in  of  the  bony  tissue  to  support  the  gum 
which  is  undoubtedly  a  new  deposit  of  process.  When  it  is  considered 
that  the  osteoblasts  are  present  in  the  peridental  membrane  throughout 
life  and  slowly  add  to  the  alveolar  wall  of  the  socket,  it  is  not  unreason- 
able to  expect  them  to  lend  their  aid  when  stimulated  and  the  irritating 
cause  is  removed. 

It  seems  probable  that  it  is  not  only  possible  to  sterilize  tissue  by 
this  perfect  circulation,  artificially  induced,  but  also  that  small  serumal 
deposits  may  be  dissolved  and  disposed  of  by  the  blood  or  possibly 
by  the  action  of  the  cells  in  these  tissues.  This  statement  does 
not  mean  that  when  the  dentist  treats  surgically  a  case  of  pyorrhea 
alveolaris,  merely  teaching  the  patient  how  to  brush  his  gums  will 
cause  the  dissolution  of  the  deposits  and  kill  the  infection.  It  is 
exceedingly  important  that  gum  brushing  should  be  taught  and  the 
patient  trained  by  repeated  lessons  until  he  acquires  this  art,  for  it 
really  is  an  art.  With  the  additional  aid  of  the  gum  brushing  the  pus 
will  soon  cease,  the  pockets  will  contract  and  close,  soreness  will  be 
relieved  and  any  small  granular  deposits  that  may  be  left  will  gradually 


278  DENTAL  PROPHYLAXIS 

disappear  as  the  tissue  hugs  up  tightly  to  the  root.  The  tissues  thus 
artificially  stimulated  seem  to  possess  five  properties.  The  first  may  be 
termed  analgesic,  or  the  relief  from  pain.  This  analgesic  action  is 
the  result  of  reducing  the  tension  and  pressure  on  nerve  terminals  from 
enlarged  and  engorged  bloodvessels.  There  is  also  a  bactericidal 
action  or  the  destruction  of  the  infection  by  increasing  the  flow  of  blood 
to  the  parts.  This  sterilizing  process  induced  in  the  cells  of  the  body 
by  a  perfect  circulation  is  well  known,  and  it  is  a  subject  of  considerable 
discussion  as  to  whether  the  action  is  produced  by  phagocytosis  or 
opsonins.  Under  artificial  stimulation  the  cells  have  also  a  solvent 
power.  That  is,  they  are  able  to  disintegrate  irritating  or  foreign 
substances.  It  is  a  well-known  fact  that  a  ligature  of  catgut  in  the 
body  is  dissolved  and  disappears.  Landois  has  shown  that  the  blood 
serum  of  every  animal  has  the  power  of  dissolving  the  blood  corpuscles 
from  a  different  species.  The  origin  of  the  solvent  which  disintegrates 
granules  of  serumal  deposits  can  only  be  conjectured,  but  it  is  a  fact 
that  they  do  disappear  as  a  result  of  perfect  circulation. 

The  eliminative  property  is  greatly  facilitated  and  permits  the 
lymphatics  to  readily  absorb  and  dispose  of  waste  products  and  irritat- 
ing substances.  There  is  also  the  nutritive  property  which  is  self 
evident,  and  is  due  chiefly  to  a  perfect  oxidizing  process.  There  is 
still  much  to  learn  concerning  these  artificial  stimulants.  If  the 
existence  of  human  beings  were  mor.^  like  that  of  animals,  this  condition 
would  be  induced  each  time  that  the  meal  of  coarse  food  was  chewed. 
Since  the  artificial  rather  than  the  animal  life  is  preferred,  and  coarse 
food  is  not  attractive,  why  should  not  this  condition  of  health  be 
produced  artificially? 

Tooth-brushes. — Opinions  vary  greatly  concerning  the  size  and  shape 
of  the  tooth-brush.  One  educator  of  the  middle  West  states  in  a  letter 
that  he  did  not  recommend  a  hair-brush,  a  nail-brush  or  a  shoe-brush 
for  brushing  the  teeth,  but  a  tooth-hru^h.  His  position  might  have 
received  serious  consideration  if  it  were  only  the  crowns  of  the  teeth 
that  were  involved,  but  as  the  brushing  of  the  gums  and  the  roof  of  the 
mouth  is  of  equal  importance  with  brushing  the  teeth,  a  brush  that  will 
adapt  itself  to  all  these  surfaces  is  the  one  to  use.  In  fact  this  process 
may  be  better  termed  mouth-brushing. 

If  cross-wise  brushing  is  indulged  in  or  a  slow  twisting  massage 
or  wiping  motion  is  employed,  the  form  and  size  of  the  brush  may  be 
varied.  Personally,  the  writer  has  not  been  able  to  secure  as  satis- 
factory results  with  either  of  these  forms  of  brushing.  The  cross-wise 
brushing  seems  to  irritate  the  festoons,  at  times  create  absorption,  and 
lacks  the  cleansing  action  upon  the  outside  surfaces.  The  wiping 
motion  with  the  sides  and  ends  of  the  bristles  is  more  cleansing  and 
the  gums  take  more  kindly  to  this  form  of  brushing,  but  this  motion  is 
necessarily  slow  and  lacks  the  stimulating  effect  produced  by  a  fast 
stroke.  When  it  is  considered  that  nature  intended  that  the  pressure 
should  be  chiefly  upward  on  the  upper  gums  and  downward  on  the 


roLiSHiNd 


m 


lower  gums,  such  as  is  induced  by  food  sliding  over  the  surfaces  of  the 
teeth  in  mastication,  it  can  be  seen  that  this  process  can  be  better 
simulated  by  a  circular  stroke  than  by  any  other.  The  gums  appear 
to  thrive  under  the  circular  stroke,  a  stimulus  is  imparted  to  the  circu- 
lation and  a  thorough  cleansing  effect  is  produced  along  the  curved 
lines  of  the  festoons  and  upon  a  third  of  the  approximal  surfaces.  A 
slow,  deliberate  stroke  is  not  as  stimulating  as  a  fast,  light  stroke. 
The  best  way  to  bring  blood  to  the  surface  of  a  tissue  in  a  short  space 
of  time  is  to  use  a  light,  rapid  massage. 

The  results  will  justify  the  means,  so  a  circular  stroke  for  the  buccal 
and  labial  surfaces  is  advised.  In  order  to  secure  the  proper  adaptation 
of  a  brush  to  the  surfaces  of  the  gums  and  the  teeth,  the  shape  of  the 
bristle  ends  of  the  brush  is  important.  Many  of  the  popular  brushes 
on  the  market  are  nearly  concave  in  shape,  having  a  long  toe  and  heel 
with  the  shorter  bristles  near  the  center.  Such  a  brush,  placed  squarely 
across  the  front  teeth,  seems  to  fit  when  at  rest,  but  if  slowly  moved 


Fig.  202 


about  the  mouth,  it  will  be  found  to  ride  in  many  places  on  the  toe 
and  heel  alone  or,  if  pressure  is  used,  these  long  bristles  ride  sidewise 
or  any  other  way.  Although  the  cranium  is  convex  in  shape,  it  has 
never  been  deemed  expedient  to  use  a  concave  hair-brush.  In  fact, 
a  concave  brush  would  not  be  as  effective  as  a  straight  one,  although  it 
might  seem  to  fit  better  when  at  rest.  A  straight-cut  tooth-brush  with 
a  slight  tuft  on  the  end  is  best  adapted  to  most  of  the  surfaces  in  most 
mouths.  The  bristles  should  be  of  sufficient  length  to  be  flexible  yet 
springy  and  stiff  enough  not  to  lose  their  life  or  spring  after  the  first 
two  or  three  days'  use.  This  necessitates  using  a  brush  with  bristles 
a  trifle  hard,  for  such  a  brush  becomes  softened  after  a  few  days'  use. 
Fig.  202  illustrates  the  two  shapes  of  brushes  just  referred  to.  When 
instructing  a  new  patient  in  the  art  of  brushing,  a  soft  brush  should  be 
recommended  to  start  with,  or  the  patient  should  be  warned  not  to 
be  too  strenuous  with  the  stiff'  brush  until  the  gums  have  had  a  chance 
to  become  tough  and  the  mucous  membrane  thickened,  otherwise 
slight  abrasions  of  the  mucous  membrane  will  be  produced,  and  a  sore 


280 


DENTAL  PROPHYLAXIS 


and  tender  surface  will  result  if  the  gums  are  brushed  at  first  with  too 
much  pressure  and  vigor  and  with  a  stiff  brush.  It  is  a  well  known  fact 
that  in  the  use  of  a  fairly  large  brush  with  three  or  four  rows  of  straight- 
cut  bristles,  set  well  apart,  the  pressure  on  any  one  point  is  consider- 
ably reduced  in  proportion  to  that  produced  by  a  shorter  and  narrower 
brush.  For  this  reason  the  best  results  from  mouth  brushing  in  adults 
may  be  obtained  when  it  is  possible  to  use  a  large  brush. 

Instructions  for  Brushing. — The  process  of  the  brushing  of  the  mouth 
may  be  divided  into  three  parts: 

First,  the  outside  or  buccal  and  labial  surfaces  of  the  teeth  and 
girnis. 

Second,  the  inside  or  palatal  and  lingual  surfaces. 

Third,  the  occlusal  or  masticating  surfaces  of  the  teeth. 


Fig.  203 


The  Buccal  and  Labial  Surfaces. — ^With  the  brush  held  in  the  hand,  as 
in  Fig.  203,  and  with  the  teeth  nearly  closed,  the  brush  is  placed  inside 
the  cheek  on  the  left  side,  so  that  the  ends  of  the  bristles  are  lightly 
in  contact  with  the  gums  over  the  upper  molars.  Now,  with  a  fast, 
circular  motion  the  brush  is  swept  backward  and  downward,  reaching 
as  far  down  on  the  lower  gums  as  the  brush  can  travel  in  this  posi- 
tion, then  forward  and  upward  as  high  on  the  gums  of  the  upper 
teeth  as  possible  (Fig.  204). 

The  brush  should  travel  in  a  perfect  circle,  not  in  an  oblong  tract, 
and  in  as  large  a  circle  as  the  vestibule  of  the  cheek  will  permit.  Very 
little  pressure  should  be  used,  for  the  stimulating  as  well  as  the  cleansing 


POLISHINO 


281 


process  is  accomplished  by  the  rapidity  of  the  stroke  and  the  direction 
traveled  by  the  ends  of  the  bristles.     Continuinjj;  this  fast,  circular 


AGE    !7 


Fig.  204 


motion  the  brush  should  be  made  to  travel  very  slowly  forward  until 
the  heel  (the  bristles  nearest  the  hand  are  called  the  heel)  engages  the 


Fig.  205 


right  cuspids.  Pausing  on  the  incisors  to  stimulate  thoroughly  the 
gums  on  both  jaws,  start  back  again  slowly  to  the  region  of  the  molars 
(Fig.  205). 


^8^ 


DENTAL  PROPHYLAXIS 


It  will  be  understood  that  the  brush  is  constantly  in  rapid  motion, 
travelling  in  a  large  circle  with  the  ends  of  the  bristles  lightly  touching 
the  gums  and  teeth. 


Fr^..  206 

Fig.  206  illustrates  the  position  of  holding  the  brush  for  the  right 
side.     On  this  side  some  persons  find  it  easier  to  maintain  a  circular 


Fig.  207 


motion  by  reversing  the  stroke,  or  brushing  from  the  lower  gums  back- 
ward and  upward.    It  makes  no  difference  in  which  direction  the  brush 


POLISHING 


283 


travels  as  long  as  the  circular  stroke  is  adhered  to.  Assuming  that  one 
is  using  the  right  hand  for  brushing,  it  will  not  be  possible  to  brush 
farther  forward  than  the  right  cuspid  teeth  (Fig.  207).  Directions  for 
brushing  the  left  side  are  applicable  to  the  right. 

Lingual  Surfaces. — 1.  Upper.  The  brush  should  be  held  as  shown 
in  Fig.  208.  The  roof  of  the  mouth  as  well  as  the  lingual  surfaces  of 
the  upper  teeth  are  brushed  with  an  in-and-out  stroke,  as  in  Fig.  209. 

The  festoons  on  the  palatal  and  lingual  surfaces  cannot  be  properly 
brushed  with  the  circular  stroke.  It  may  be  noted  that  they  assume  a 
much  straighter  line  than  on  the  buccal  and  labial  surfaces.  Therefore 
the  bristles  travelling  in  and  out  with  this  straight  line  reach  all  sur- 
faces and  are  stimulating  and  non-irritating  in  their  action. 


Fig.  208 


The  ends  of  the  bristles  should  be  placed  against  the  gums  of  the  right 
molar  teeth,  and  the  brush  drawn  straight  forward  until  the  heel  wipes 
the  lingual  surfaces  of  the  right  incisors  and  cuspids  and  protrudes 
from  the  mouth  for  a  short  distance.  The  upper  lip  should  be  drawn 
downward  to  prevent  the  moisture  from  being  thrown  outward  by  the 
snap  of  the  bristles  passing  over  the  edges  of  the  incisors.  The  brush  is 
now  pushed  straight  back  again  on  the  gums  and  this  in-and-out  stroke 
is  rapidly  made  and  confined  on  this  surface  for  a  few  seconds.  This 
fast  in-and-out  stroke  of  the  brush  is  kept  up  and  carried  across  the 
roof  of  the  mouth  until  all  of  the  hard  palate  is  covered  and  the  gums 
on  the  left  side  of  the  mouth  are  reached.  Here  the  in-and-out  stroke 
is  applied  rapidly  for  a  few  seconds,  as  far  back  as  the  distal  surfaces  of 


284 


DENTAL  PROPHYLAXIS 


the  third  molars.  The  same  stroke  should  be  used  on  the  return,  the 
palate  should  be  crossed  to  the  right  side  again,  and  again  back  to 
the  left  side.  Special  care  should  be  used  to  reach  the  gums  around 
the  last  molars,  as  there  is  a  tendency  not  to  brush  back  far  enough. 


Fig.  203 


2.  Loicer  Lingual  Surfaces. — The  lingual  surfaces  of  the  lower  teeth 
are  the  most  difficult  to  brush  and  it  requires  quite  a  little  practice  before 


Fig.  210 


the  gums,  especially  on  the  right  side,  can  be  deftly  reached.  Nineteen 
out  of  twenty  mouths  will  disclose  a  congested  gingival  border  on 
the  lingual  surfaces  of  the  right  lower  molars,  and  in  order  that  the  wrist 


POLISHING 


28: 


may  bend  freely  so  that  the  toe  of  the  brush  may  reach  this  surface, 
it  is  suggested  that  the  brush  be  held  in  the  hand  as  in  Fig.  210. 

These  gum  surfaces  are  brushed  almost  entirely  with  the  toe  or  tuft 
of  the  brush,  the  motion  being  a  fast  in-anrl-out  stroke,  similar  to  that 


Fig.  211 


used  on[the  hard  palate,  as  in  Fig.  211.  Starting  on  the  right  side  with 
the  bristles  of  the  tuft  resting  on  the  gum  next  to  the  last  molar,  the 
brush  is  drawn  forward.  In  this  case  the  bristles  at  the  heel  do  not 
sweep  the  lower  incisors  as  the  handle  of  the  brush  is  tipped  slightly 
upward. 


Fig.  212 


The  brush  is  now  forced  backward  in  the  same  line,  leaning  slightly 
toward  the  tongue,  and  the  in-and-out  stroke  is  applied  rapidly  to 
this  surface.  Maintaining  always  this  fast  stroke,  and  slowly  coming 
forward,  the  handle  of  the  brush  is  now  raised  to  a  sharp  angle  and  the 
gums  below  the  incisors  are  brushed  with  an  up-and-down  stroke. 


286  DENTAL  PROPHYLAXIS 

going  back  and  forth  across  them  several  times.  Continuing  the  in- 
and-out  stroke  the  tuft  is  adapted  to  the  gums  of  the  left  side  and  they 
are  brushed  in  a  manner  similar  to  that  described  for  the  right  side, 
again  slowly  returning  to  the  right  and  repeating  once  more  to  the  left 
side.  A  slight  gagging  sensation  will  sometimes  be  felt  in  trying  to 
reach  as  far  back  as  the  brush  should  actually  go,  but  with  persistent 
practice  this  can  be  greatly  overcome  in  a  short  time. 

Masticating  Surfaces. — Lastly  the  masticating  surfaces  should  be 
brushed  in  order  to  remove  any  food  debris  in  the  fissures  or  sulci  of 
the  molars  and  bicuspids.  The  tuft  of  the  brush  should  also  be  carried 
to  the  distal  surfaces  of  the  last  molars  on  both  the  upper  and  lower 
jaws  and  with  a  wiping  or  twisting  motion  these  surfaces  should  be 
cleansed. 

The  foregoing  description  of  brushing  gives  but  a  stereotyped  form. 
The  mouth  should  be  gone  over  three  or  four  times  until  the  gums 
begin  to  tingle  and  a  slight  sense  of  numbness  is  felt. 

In  the  roof  of  the  mouth  are  the  posterior  and  anterior  palatine 
arteries  which  help  to  supply  the  gum  tissue,  hence  the  importance  of 
brushing  the  hard  palate  (Fig.  212). 

It  should  be  noted  that  the  brush  is  Used  with  a  full-arm  motion 
and  that  a  fast  but  light  stroke  is  essential  to  secure  the  desired  results. 

Number  of  Daily  Brushings. — Not  so  very  many  years  ago  more  than 
one  bathtub  in  a  private  houst^  was  considered  a  luxury.  Today  it 
is  realized  that  frequent  bathing  is  a  necessity. 

Some  dentists  advise  their  patients  to  brush  their  teeth  before 
retiring;  some,  night  and  morning;  and  the  patient  who  followed  this 
last  rule,  thought  himself  virtuous  indeed.  The  matter  of  brushing 
the  teeth  is  purely  educational  and  resolves  itself  into  a  habit.  Time 
can  always  be  found  for  any  habit — it  is  merely  a  question  of  what 
habits  are  acquired. 

After  each  meal  a  certain  amount  of  food  is  retained  on  the  surfaces 
of  the  teeth.  In  less  than  an  hours'  time  this  food  begins  to  decom- 
pose. If  the  teeth  are  brushed  at  night  and  in  the  morning  before 
breakfast,  remnants  of  the  breakfast  remain  on  the  teieth  until  bed- 
time, joined  through  the  day  by  those  of  lunch  and  dinner.  There 
may  be  some  arguments  in  favor  of  not  disturbing  the  decomposing 
food  in  the  mouth  all  day,  but  such  arguments  are  usually  based  on 
the  statement  that  people  do  live  with  unbrushed  teeth,  so  why  handi- 
cap them  with  an  extra  daily  duty  when  they  have  so  little  time  to 
spare.  Those  who  advance  these  arguments  usually  have  a  breath 
far  from  pleasing.  It  cannot  be  shown  scientifically  that  a  mouth 
containing  decomposing  food  is  as  healthy  and  wholesome  as  one  that 
is  free  from  it. 

The  teeth  should  be  thoroughly  cleaned  after  each  meal  with  brush 
and  dentifrice,  and  given  a  vigorous  brushing  with  clear  water  the 
first  thing  in  the  morning.  This  means  four  brushings  a  day.  Of 
course  it  is  not  always  possible  to  follow  this  rule  to  the  letter,  but  where 
one  has  access  to  a  bowl  and  one's  tooth-brush,  the  teeth  should  be 


POLISHING  287 

cleaned.  All  children  should  be  taught  this  habit,  as  there  can  be  no 
greater  insurance  for  health  and  freedom  from  infectious  diseases 
than  a  mouth  free  from  decomposing  food. 

Dentifrices. — The  most  important  ingredient  in  a  dentifrice  is  soap. 
Next,  a  mild  abrasive,  such  as  a  fine  grade  of  precipitated  chalk. 
The  rest  ot  the  formula  is  of  but  little  value  and  is  used  chiefly  to  dis- 
guise the  soap  and  impart  a  pleasant  taste.  The  removal  of  grease  is 
a  chemical  action  and  soap  is  essential  for  thoroughly  cleaning  the 
teeth.  If  fat  is  rubbed  on  the  hands  or  on  a  slab  of  glass  it  will  be 
difficult  to  remove  it  with  clear  water  and  a  brush.  Although  with 
considerable  effort  it  may  be  done,  soap  will  remove  it  much  more 
quickly.  A  fine  grade  of  powdered  Castile  soap  is  the  best,  but  it  is 
seldom  found  in  the  preparations  on  the  market,  as  it  does  not  give 
sufficient  lather  to  suit  either  manufacturer  or  purchaser.  The  most 
harmful  constituent  in  a  dentifrice  is  a  gritty,  coarse  grade  of  chalk. 
The  teeth  should  be  cleaned,  not  scoured,  and  the  daily  use  of  a  gritty 
dentifrice  will  eventually  cause  abrasion  of  the  thjn  enamel  surfaces 
at  the  necks  of  the  teeth.  In  fact  some  preparations  contain  pumice 
and  in  one  foreign  production,  powdered  oyster  shells  were  found. 
The  grit  may  be  readily  detected  by  placing  some  of  the  paste  or  powder 
between  th:e  teeth  and  biting  on  it.  Finer  tests  may  be  made  by  putting 
it  between  two  glass  surfaces,  rubbing  them  together  and  examining 
them  with  a  magnifying  glass, 

A  mild  abrasive  is  helpful  in  the*  removal  of  the  slippery  film  of 
mucin  and  viscid  accretions  on  the  surfaces  of  the  teeth.  Its  daily  use 
is  harmless  providing  the  grit  is  fairly  soluble  and  not  coarse.  When 
one  computes  the  number  of  occlusions  that  take  place  daily  between 
the  masticating  surfaces  of  the  teeth  during  the  three  meals  and  notes 
what  little  wear  of  the  enamel  cusps  is  exhibited  at  thirty-five  or  forty 
years  of  age,  it  may  be  concluded  that  the  use  of  a  fine  grade  of  precipi- 
tated chalk  as  a  base  for  a  dentifrice  is  not  a  serious  menace  to  the 
enamel  tissue.  There  is  but  little  choice  between  powder  and  paste, 
as  regards  efficiency.  Powder  has  to  be  worked  into  a  past-like 
condition  in  the  mouth  with  the  brush,  while  paste  quickly  spreads 
itself  over  the  teeth  for  immediate  action.  The  majority  of  people 
find  the  paste  much  more  pleasant  to  use.  The  difference  in  the  f  ormulse 
of  the  two  preparations  consists  in  leaving  out  the  saccharin  in  the 
powder  and  mixing  the  powders  and  oils  with  glycerin  to  form  paste. 

A  simple,  cheap  and  effective  power  may  be  made  by  placing  the 
following  ingredients,  all  of  which  may  be  bought  at  any  drug-store, 
in  a  quart  Mason  jar: 

Finest  grade  English  precipitated  chalk h  pound 

Powdered  Castile  soap If  ounces 

Light  carbonate  of  magnesia \  ounce 

Oil  of  clove 46    drops 

Oil  ol  wintergrecn 35         " 

Oil  of  sassafras 35         " 

Oil  of  peppermint   ...            18        " 

Saccharin — finely  powdered 4    grains. 


288 


DENTAL  PROPHYLAXIS 


The  glass  top  should  be  securely  fastened  and  the  contents  shaken 
vigorously.  The  mixing  process  takes  some  time  as  it  takes  at  least 
twenty-four  hours  for  the  oils  to  permeate  the  powders,  but  the  jar 
may  be  picked  up  at  varying  intervals  and  its  contents  thoroughly 
shaken.  A  larger  bottle  with  the  same  quantity  of  powder  will  permit 
of  a  more  thorough  mixing  in  a  shorter  time. 

The  brush  should  be  very  wet  when  the  powder  is  placed  upon  it 
and  care  should  be  taken  not  to  inhale  when  introducing  the  brush  into 
the  mouth. 

A  properly  prepared  tooth  paste  is  a  much  more  pleasant  toilet  article 
to  use  and,  as  there  are  some  on  the  market  quite  effective  and  harm- 
less, one  of  these  may  be  recommended  to  patients. 


Fig.  213 


Each  tooth  has  five  surfaces.  Three  of  these  can  be  cleaned  with 
the  brush,  but  the  two  approximal  surfaces,  the  most  susceptible  of 
all,  cannot  be  reached  with  it.  In  other  words  three-fifths  of  the  sur- 
faces of  the  teeth  can  be  cleaned  with  the  tooth-brush  but  not  the 
remaining  two-fifths  which  most  need  it.  It  should  then  be  apparent 
that  if  all  the  food  is  to  be  cleaned  off  all  the  surface  of  all  the  teeth, 
additional  means  of  so  doing  must  be  employed.  Up  to  the  present 
time  nothing  is  known  that  will  accomplish  this  more  efficiently  and 
harmlessly  than  the  floss  silk  and  a  mouth  wash  of  lime  water. 

Floss  Silk. — If  the  floss  silk  is  skilfully  and  frequently  used,  the 
approximal  surfaces  may  be  kept  quite  free  from  dental  caries.  To 
induce  patients  to  use  the  floss  silk  with  regularity  is  a  task,  but  by 
being  persistent  in  requesting  and  logical  in  the  reason  for  its  use,  they 
may  be  made  gradually  to  acquire  the  floss  habit.  To  insure  the  proper 
use  of  the  floss  the  fillings  in  the  approximal  surfaces  should  be  smooth 


POLISHING 


289 


and  polished,  with  just  sufficient  pressure  at  the  contact  points  to  allow 
the  floss  to  snap  through  without  too  much  effort  in  forcing  it.  The 
patient  should  be  instructed  not  to  allow  the  floss  to  snap  through  on 


Fig.  214 


the  gum  tissue  hard  enough  to  wound  it.     There  is  but  little  danger 
of  this  after  practice,  especially  af-^n  the  gums  have  become  hard  and 


Fig.  215 


tough  from  brushing.     A  reasonably  small-sized  waxed  floss  is  the  best 
to  use.     For  adults  the  piece  should  be  fourteen  or  fifteen  inches  in 
length.    The  end  of  the  floss  is  taken  between  the  thumb  and  first 
19 


290 


DENTAL  PROPHYLAXIS 


finger  of  the  left  hand  and  two  wraps  made  around  the  end  of  the  first 
finger,  and  this  act  repeated  with  the  other  end  of  the  floss  on  the 
right  forefinger.     The  floss  is  now  held  securely  and  will  permit  the 


Fig.  217 


POLISHING  291 

ends  of  the  two  thumbs  or  the  two  second  fingers  or  a  coml)ination  of 
a  thumb  of  one  hand  and  a  second  finger  of  the  other,  to  guide  the  silk 
into  its  position  in  the  mouth  and  force  it  between  the  teeth.  Fig. 
213  shows  adaptation  of  floss  for  right  upper  teeth.  Fig.  214  shows 
adaptation  for  left  upper  teeth.  Fig.  215  shows  adaptation  for  all 
the  lower  teeth.  After  the  floss  has  passed  through  the  contact  points 
it  should  be  rubbed  back  and  forth  against  both  approximal  surfaces 
to  polish  them  mechanically.  In  withdrawing  the  floss,  if  the  end  held 
opposite  the  lingual  surface  is  brought  over  on  the  buccal  surface  and 
the  silk  is  pulled  through  the  contact  points  in  the  form  of  a  loop,  it 
will  be  more  effective  in  polishing  or  cleaning  these  surfaces  than  if 
merely  snapped  out  (Figs.  216  and  217).  The  floss  will  not,  however, 
thoroughly  remove  all  the  food  between  the  teeth,  therefore  we  must 
have  recourse  to  a  mouth  wash. 

Lime-water. — Practically  all  the  mouth  washes  on  the  market  are 
formulated  to  accomplish  two  results:  First,  a  neutralizing  action, 
either  acid  or  alkaline,  and  second,  a  germicidal  action.  It  will  readily 
be  understood  that  the  latter  result  cannot  be  obtained  in  the  mouth, 
while  the  former  is  immaterial.  In  order  to  secure  immunity  to  decay, 
the  bacteria  must  be  robbed  of  any  pabulum  upon  which  to  feed  and 
any  plaques  or  glue-like  accumulations  on  the  surfaces  of  the  teeth 
must  be  dissolved. 

Acid  mouth  washes  have  been  advocated  because  it  has  been  found 
that  the  lactic  acid  forming  bacteria*4/e  retarded  in  their  growth  and 
activity  in  an  acid  medium.  Alkaline  washes  have  been  prescribed 
because  of  the  belief  that  they  will  neutralize  any  lactic  acid  formed 
that  will  induce  caries.  Both  of  these  theories  are  based  on  partial 
facts  only,  for  it  has  been  absolutely  proved  that  the  chemical  action 
of  an  acid  or  an  alkali  used  as  a  mouth  wash  for  neutralizing  purposes 
will  not  inhibit  dental  caries  to  any  great  degree.  All  of  these  washes 
are  supposed  to  contain  germicides  that  will  imimediately  destroy  the 
microorganisms  of  the  mouth.  This  is  of  course  untrue,  especially 
when  the  short  time  they  are  retained  in  the  mouth  for  this  purpose  is 
considered.  The  peroxide  of  hydrogen  is  religiously  used  by  many, 
in  the  belief  that  the  oxygen  liberated  is  a  germicide  of  sufficient  power 
to  destroy  all  the  bacteria.  The  mechanical  action  of  the  peroxide  in 
its  boiling  process,  while  it  does  liberate  the  oxygen,  is  more  effective 
in  dislodging  particles  of  food  debris  around  the  necks  of  the  teeth  than 
in  its  germicidal  action  on  the  organisms  in  the  mouth.  In  the  study 
of  dental  caries  it  must  be  concluded  from  the  present  knowledge  of  the 
subject  that  in  the  main  Professor  Miller's  theory  still  holds  good, 
namely,  that  the  exciting  cause  is  due  to  the  production  of  lactic  acid 
by  the  action  of  microorganisms  on  carbohydrates,  and  that  decay 
takes  place  most  readily  on  those  surfaces  least  exposed  to  friction 
during  mastication,  such  as  the  fissures  or  pits,  approximal  surfaces, 
and  the  necks  of  the  teeth.  Dr.  J.  Leon  Williams  was  the  first  to  point 
out  the  fact  that  a  thin  gelatinous  plaque  was  first  formed  on  the 


292  DENTAL  PROPHYLAXIS 

surface  of  the  enamel  and  under  and  in  this  thin  film  the  bacteria 
obtained  a  secure  position  that  made  their  dislodgement  difficult. 
Their  action  in  the  production  of  acid  was  intensified  when  thus 
protected.  Other  scientific  investigators  have  corroborated  Williams' 
observations.  Laying  aside  any  theories  regarding  susceptibility  and 
immunity,  it  must  be  admitted  that  the  battle  just  now  should  be  the 
thorough  removal  of  all  food  debris  and  the  removal  of  these  plaques 
and  glue-like  accretions. 

The  mucin,  which  is  a  product  of  the  salivary  and  mucous  glands, 
plays  an  important  part  in  the  formation  of  these  plaques,  and  it  is 
precipitated  from  the  secretions  in  the  mouth  by  the  presence  of  an 
acid.  This  precipitate  forms  on  the  surfaces  of  the  teeth  and  becomes 
the  factor  in  incasing  the  bacteria  with  food  debris  and  in  forniing  the 
so-called  plaques.  Mucin  thus  precipitated  is  soluble  in  or  may  be 
dissolved  by  an  alkali.  It  has  been  found  that  the  presence  of  fruit  acids 
in  the  mouth  stimulates  the  salivary  secretions  in  amount  and  alkalinity. 
It  is  claimed  by  some  investigators  that  the  increased  alkalinity  of  the 
saliva  has  a  solvent  action  on  the  precipitated  mucin  and  a  neutralizing 
action  on  lactic  acid  and  thus  becomes  a  natural  preventive  of  dental 
caries.  Other  investigators  have  as  yet  been  unable  to  find  that  the 
alkalinity  so  produced  is  of  sufficient  strength  to  have  this  solvent 
action.  Again,  it  is  claimed  that  the  acids  of  fruits  have  a  curdling 
effect  on  the  mucin,  forming  it  into  flakes  which  are  easily  removed 
from  the  tooth  surfaces.  ^ 

There  is  a  serious  question  concerning  the  habitual  use  of  these 
acids  for  this  purpose.  Prinz  states,  as  his  opinion,  that  the  correct- 
ness of  the  use  of  acid  mouth  washes  is  not  substantiated  by  clinical 
experience,  that  the  pharmacological  principle  evolved  in  the  selection 
of  such  solutions  is  erroneously  applied,  that  constant  forcible  stimula- 
tion of  the  salivary  glands  by  acids  is  followed  by  an  impairment  of 
glandular  function  and  that  the  acidity  of  the  solution  kills  the  im- 
portant salivary  ferments.  A  reasonable  amount  of  fruit  is  healthful 
and  desirable,  but  dentifrices  and  mouth  washes  containing  fruit  acids, 
must  be  used  with  considerable  judgment. 

The  most  cleansing  and  the  least  harmful  of  all  fruits  is  the  apple. 
This  with  its  dense  texture  acts  as  a  mechanical  cleanser,  and  the  malic 
acid  is  comparatively  harmless.  Where  it  is  impossible  to  have 
access  to  a  tooth-brush  the  eating  of  an  apple  will  be  found  an  excellent 
substitute. 

If  it  can  be  scientifically  shown  that  dentifrices  and  mouth  washes 
containing  fruit  acids  in  certain  proportions  are  harmless  to  the  teeth 
and  the  tissues  of  the  mouth  and  are  superior  to  any  of  the  present-day 
preparations  as  prophylactic  agents  for  dental  caries,  it  would  prove 
to  be  a  valuable  contribution  to  dental  prophylaxis. 

As  it  will  take  a  number  of  years  to  demonstrate  this  as  a  fact  it  will 
be  necessary  for  the  present  to  adhere  to  those  agents  that  have  proved 
themselves  to  be  harmless  and  efficient  in  the  past. 


POLISHING 


293 


There  is  a  harmless  solvent  for  the  mucin  on  the  surfaces  of  the  teeth 
that  is  quite  positive  in  its  action.  This  solvent  is  lime-water,  and  is 
made  from  the  coarse  calcium  oxid  or  unslaked  lime.  Its  preparation 
is  simple  and  cheap,  and  when  its  efficiency  for  the  use  and  purpose 
intended  is  considered,  it  will  rank  as  an  important  agent  for  the  pre- 
vention of  dental  caries. 

Some  coarse  lime,  such  as  is  used  in  making  rough  plaster,  may  be 
secured  from  a  paint  store  or  from  a  mason.  The  refined  product 
found  in  the  drug-stores  apparently  does  not  have  the  same  effect. 
The  refining  process  robs  it  of  some  of  its  beneficial  properties.  It  is 
cream  white  in  color.  The  lumps  should  be  broken  up  into  coarse 
powder  and  a  half-cupful  put  into  a  quart  bottle.  The  bottle  should 
be  nearly  filled  with  cold  water,  room  enough  being  left  to  permit  of 


Fig.  218 


thorough  shaking,  shaken  vigorously  and  set  aside  for  three  or  four 
hours  to  allow  the  lime  to  settle.  Then  as  much  of  the  clear  water  as 
possible  should  be  poured  ofP,  for  this  contains  the  washings  of  the 
lime.  It  will  be  found  impossible  to  pour  off  all  the  water  without 
losing  some  of  the  lime,  but  by  pouring  slowly  nearly  two-thirds 
may  be  drawn  off.  The  bottle  can  then  be  filled  with  cold  water 
and  shaken  thoroughly,  when,  after  it  has  settled  again,  it  will  be 
ready  for  use.  A  bottle  of  convenient  size  should  be  procured;  one 
holding  ten  or  twelve  ounces,  and  filled  with  the  clear  water  from  the 
large  bottle.  This  smaller  bottle  will  be  more  convenient  to  use  at 
the  bowl.  The  large  bottle  can  be  again  filled  with  cold  water,  shaken 
thoroughly  and  set  aside  to  be  used  as  needed  (Fig.  218).  This 
operation  may  be  repeated  over  and  over  again,  for  the  original  half- 
cupful  of  lime  will  make  five  or  six  quarts  of  lime-water.     If  the  first 


294  DENTAL  PROPHYLAXIS 

use  of  the  wash  proves  that  it  is  a  little  strong,  it  can  be  diluted  in  the 
small  bottle.  With  new  patients  and  those  having  tender  gums  it  may 
have  to  be  diluted,  but  as  soon  as  possible  it  should  be  used  undiluted. 
When  taken  into  the  mouth  it  should  be  forced  back  and  forth  vigor- 
ously between  the  teeth  with  the  tongue  and  cheeks  and  the  rinsing 
continued  until  it  breaks  into  a  foam.  Not  that  there  is  any  particu- 
larly beneficent  action  to  the  foaming,"  but  if  it  is  worked  through  the 
teeth  long  enough  to  make  the  foam  it  will  have  been  in  contact  with 
the  surfaces  of  the  teeth  long  enough  to  have  a  disorganizing  action 
on  the  mucin  and  plaques.  Afterward  the  mouth  should  be  thor- 
oughly rinsed  with  warm  water  to  take  away  the  taste  of  the  lime- 
water.  It  is  the  unpleasant  taste  of  the  lime  that  makes  it  difficult  to 
induce  the  patients  to  use  it  at  the  start,  but  after  a  short  time  the 
cleansing  effect  is  so  pleasing  that  they  soon  forget  about  the  taste. 
It  may  be  flavored  with  saccharin  or  any  flavoring  material,  but  this 
will  hardly  be  found  necessary.  The  lime-water  should  be  used  after 
the  brushing  and  flossing,  after  each  meal. 

Diet. — The  greater  part  of  this  chapter  has  been  devoted  to  a  detailed 
description  of  the  operative  procedure  for  dental  hygienists  to  follow 
and  the  instructions  for  home  care  of  the  mouth  which  she  is  to  teach. 

It  must  not  be  assumed  that  the  foregoing  is,  therefore,  the  most 
important  part  of  dental  prophylaxis.  On  the  contrary,  the  hygienist 
will  find  by  experience  that,  despite  the  most  conscientious  effort  on 
her  part,  there  will  be  mouths  ilf  which  dental  caries  is  never  under 
control.  In  these  cases  it  will  be  found  that  the  diet  is  such  as  to 
counteract  the  most  painstaking  care  on  the  part  of  the  patient  and 
hygienist.  It  may  be  truthfully  stated  that,  aside  from  the  influence 
of  heredity,  the  controlling  factors  in  mouth  health  are  diet  and  extreme 
cleanliness. 

The  most  important  study  of  the  dental  hygienist  should  be  that  of 
foods,  and  the  influence  which  she  can  have  on  mothers  and  children 
in  this  respect  will  be  her  most  important  educative  service.  The 
subject  of  foods  must  be  studied  in  great  detail,  and  it  is  possible 
in  this  chapter  to  mention  only  the  most  salient  points  regarding  the 
relation  of  the  dietary  to  the  teeth. 

During  infancy  and  childhood,  the  important  single  substance  for  the 
growth  of  bones  and  teeth  is  calcium  phosphate,  and  the  amount  of 
calcium  available  for  tooth  formation  regulates  whether  the  enamel  be 
hard  and  dense  or  relatively  soft  and  porous.  The  influence  of  diet 
and  its  relation  to  the  teeth  must  therefore  begin  with  pregnancy. 
Before  birth  and  for  some  time  thereafter,  if  the  infant  is  nursed  at  the 
breast,  the  high  calcium  requirement  of  infancy  is  supplied  by  the 
mother.  Her  calcium  requirements  are  consequently  increased,  and 
unless  extra  lime  is  present  in  her  diet,  her  teeth  and  skeleton  may 
suffer.  Milk,  which  is  a  perfect  food,  contains  all  the  necessities  for 
infant  growth,  but  when  milk  ceases  to  be  the  sole  article  of  food, 
the  new  diet  is  most  important.     Especial  emphasis  should  be  placed 


POLISHING  295 

on  foods  that  are  high  in  calcium  content  as  soon  as  the  temporary 
teeth  have  erupted.  Some  of  the  most  important  of  tiiese  foods  are 
milk, buttermilk, cheese,  celery,  spinach,  turnips,  radishes,  string  beans, 
parsnips,  carrots,  kidney  beans,  cabbage,  cauliflower,  onions,  etc. 
It  is  also  present  in  the  various  whole  grains  and  it  is  well  to  note 
that  the  more  highly  refined  the  grain  is,  the  less  calcium  it  contains. 

Alfred  W.  McCann,  in  his  book  This  Famishing  World,  says:  "The 
unrefined  grain  of  wheat  as  it  comes  from  the  field  contains  in  organic 
form  the  twelve  mineral  substances  needed  for  the  health,  growth  and 
life  of  the  body.  White  bread  becomes  white  because  from  the  ground 
grain  of  wheat  three-fourths  of  the  mineral  salts  and  colloids,  including 
the  salts  of  calcium,  phosphorus,  iron,  potassium,  chlorine,  fluorine, 
sulphur,  magnesium,  manganese,  etc.,  are  removed.  These  mineral 
substances  are  contained  in  the  brown  outer  skin,  the  cells  underneath 
this  skin  and  the  germ  of  the  wheat  berry.  They  are  sifted  and  bolted 
out  of  the  ground  meal,  leaving  behind  the  white,  starchy  cells  and  the 
refined  gluten  of  the  interior  part  of  the  berry." 

All  of  our  cereal  foods,  such  as  rice,  corn  and  oats,  are  demineralized 
during  a  refining  process  which  should  never  be  permitted.  The 
hygienist  has  a  mosi  important  duty  in  educating  people  in  the  use  of 
natiu-al  refined  grains. 

Inorganic  calcium  is  present  in  drinking  water  and  in  lime-water 
and  can  be  absorbed  from  them  ir^  mall  quantities.  It  is  interesting 
to  note,  however,  that  a  quart  of  milk  contains  more  absorbable 
calcium  than  a  quart  of  clear  saturated  lime-water,  and  that  milk 
used  freely  as  food  in  youth  is  the  most  practical  means  of  insuring 
an  abundance  of  calcium  in  the  dietary.  The  diet  depends  so  much 
upon  the  digestive  capacity  of  the  child,  that  in  some  cases  calcium 
is  not  utilized  correctly  because  of  some  digestive  disturbance.  The 
most  common  is  that  caused  by  the  ingestion  of  too  much  sugar  which 
frequently  causes  digestive  disturbances  unfavorable  to  the  absorption 
of  the  necessary  amounts  of  calcium. 

McCann  says:  "Sugar  and  calcium  possess  a  remarkable  affinity 
for  each  other.  When  refined  sugar  or  glucose,  both  of  which  are 
mineral-free  and,  therefore,  like  distilled  water,  mineral-hungry,  are 
consumed  in  generous  quantities  they  attack  the  soluble  calcium 
of  the  tissues.  The  tissues  retaliate  in  turn  by  sapping  the  calcium  of 
the  blood.  The  blood,  which  demands  a  minimum  calcium  content, 
with  never  relaxing  energy,  steals  calcium  from  the  teeth  and  bones. 
The  experiments  of  Voit  and  others  prove  this.  Children  will  suffer 
and  prospective  mothers  decline  as  long  as  they  consume  an  excess  of 
refined  or  denatured,  mineral-free  sugar,  glucose  and  starch  in  their 
diet  or  as  long  as  food  industries  continue  to  remove  the  soluble  mineral 
elements  from  the  chief  sources  of  their  food  supply." 

In  fact  when  the  diet  of  the  average  American  child  is  considered, 
it  is  not  so  astonishing  to  find  that  dental  caries  is  a  universal 
malady.  Originating  as  it  does  from  carbohydrate  fermentation  upon 


296  DENTAL  PROPHYLAXIS 

the  teeth,  no  other  result  could  be  expected  among  the  children  of 
a  nation  averaging  nearly  one  hundred  pounds  of  sugar  per  capita 
per  year.  The  writer  personally  believes  that  in  childhood,  a  well 
balanced  diet,  with  special  emphasis  upon  the  calcium  content  foods, 
and  the  elimination  of  free  sugar  would  result  in  practical  immunity 
from  dental  caries,  even  in  the  absence  of  a  rigid  system  of  mouth 
cleanliness.  The  causes  of  susceptibility  and  immunity  are  still 
under  investigation,  but  it  is  reasonable  to  believe  that  suscep- 
tibility is  mainly  in  proportion  to  the  consumption  of  free  sugar,  and 
that  immunity  is  acquired,  in  a  great  measure,  by  the  absence  of 
free  sugar  in  the  dietary.  When  it  is  considered  that  dental  caries 
can  only  be  produced  from  starch  and  sugar,  and  that  the  starch  must 
be  reduced  to  dextrose  before  it  can  be  converted  into  lactic  acid,  it  is 
quite  truthful  to  make  the  statement  that  all  dental  decay  is  produced 
by  sugar.  Clinical  experience  and  general  observation  seem  to  show, 
however,  that  the  high  consumption  of  starchy  food,  if  unaccompanied 
by  free  sugar  does  not  result  in  dental  decay.  In  fact  the  evidence  is 
all  against  the  sugar.  Among  the  peasant  classes  of  Italy,  Greece, 
the  Balkan  States,  Germany,  and  others  where  the  diet  consists  mainly 
of  coarse  foods,  vegetables  and  fruits,  but  where  free  sugar  is  a  luxury 
and  cannot  be  indulged  in,  decayed  teeth  are  the  exception  and  not 
the  rule.  This  is  also  true  of  the  Esquimos,  the  African  Negroes,  the 
American  Indians,  the  Maoris  of  !)4^w  Zealand,  and  many  of  the  South 
Sea  Islanders. 

Free  sugar  consumption  in  Italy  averages  but  thirteen  pounds 
per  capita  per  year — less  than  a  teaspoonful  a  day.  The  American 
mother  would  be  inclined  to  question  an  average  of  about  one  hundred 
pounds  per  capita  per  year  in  this  country,  but  few  realize  the  enormous 
amount  used  weekly  in  the  average  home  for  cooking  alone,  not  to 
mention  the  quantity  utilized  in  preserving  fruits. 

The  medical  profession  is,  to  a  great  extent,  responsible  for  this 
situation,  for  the  family  physician  has  taught  mothers  to  believe  that 
free  sugar  is  an  essential  food  for  growing  children.  Under  the  existing 
conditions  what  chance  h,as  an  American  child  to  have  sound  teeth? 
If  he  is  a  modified  milk  baby,  sugar  is  added  to  the  milk,  in  the  pro- 
portion of  one  ounce  in  twenty,  at  only  a  few  weeks  after  birth,  and  all 
too  frequently  cane  sugar  takes  the  place  of  milk  sugar.  The  taste 
and  craving  for  sweetened  foods  is  developed  at  once  and  is  steadily 
encouraged  as  he  progresses  to  cereals  with  sugar,  puddings,  jellies, 
sweetened  crackers,  etc.  To  the  normal  sugar  supply  found  in  milk, 
vegetables  and  fruits,  and  in  the  conversion  of  starchy  foods,  is  added 
an  ever  increasing  amount  of  free  sugar  at  meal  time,  augmented 
between  meals  by  sqda  water,  ice-cream  and  candy.  The  sugar  con- 
sumption is  so  excessive  that  the  liver  is  overloaded  with  glycogen  and 
it  is  verypossible  that  herein  lies  the  secret  of  the  child's  susceptibility; 
not  only  in  the  fermentation  of  the  sugar  on  the  tooth,  but  also  in  the 
action  of  osmotic  forces  through  the  enamel  with  the  blood  and  body 


POLISHING  297 

juices  which  are  surcharged  with  glucose  and  the  absorbed  products  of 
fermented  surplus  glucose  from  the  intestines.  There  can  be  but  one 
result;  the  deciduous  teeth  are  attacked  by  dental  caries,  and  at  the 
beginning  of  his  school  life  the  child  presents  a  wrecked  mouth  and  it  is 
only  a  matter  of  time  before  the  permanent  teeth  are  similarly  affected. 

And  so  the  medical  profession,  by  advocating  free  sugar  as  part  of 
the  diet,  is  constantly  creating  a  disease  known  as  dental  caries  which 
demands  a  specialty  known  as  dentistry.  Dentistry,  in  turn,  has 
filled,  crowned  and  capped  these  decayed  teeth  in  innocence  and 
ignorance  of  the  bacterial  colonies  which  exist  on  the  ends  of  the  roots 
of  pulpless  teeth,  causing  secondary  infections  of  the  heart,  kidneys, 
joints  and  other  organs  and  tissues  of  the  body,  thus  returning  the 
compliment  to  the  medical  profession  by  creating  thousands  of  cases 
of  systemic  infection  to  be  given  over  to  its  care  and  treatment — with 
the  public  as  the  victim.  Neither  the  medical  nor  the  dental  profession 
has  realized  that  this  vicious  circle  existed,  but  no  great  reduction  can 
be  made  in  dental  caries  and  resultant  systemic  infections  until  this 
circle  is  broken. 

The  dental  hygienist  must  be  the  one  to  break  this  circle,  by  teaching 
American  mothers  who  have  for  generations  been  educated  to  look  upon 
free  sugar  as  a  food,  that  free  sugar  is  the  chief  cause  of  dental  decay 
and  that  dental  decay  is  the  chief  cause  of  many  of  the  serious  illnesses 
of  childhood  and  adult  life.  Until  the  time  comes  when  these  truths 
are  generally  recognized,  the  effort  must  be  made  to  counteract  the 
evil  effects  of  a  faulty  diet  by  a  rigid  system  of  mouth  cleanliness  to 
lessen  the  carbohydrate  fermentation.  The  sugar  consumption  has 
increased  amazingly  during  the  past  forty  years,  and  if  dentistry,  as  a 
science,  had  not  advanced  so  rapidly  during  the  same  period,  ruined 
mouths  would  be  even  more  prevalent. 

The  soft  pappy  foods,  which  very  often  constitute  the  bulk  of  the 
diet  of  younger  children,  require  so  little  mastication  as  to  seriously 
hamper  the  normal  development  of  the  jaws,  face,  and  even  the  brain 
case  itself.  It  may  also  be  well  to  mention  the  deleterious  effect  on 
the  enamel  of  the  teeth,  of  skin  diseases,  especially  if  contracted  during 
early  childhood.  It  is  very  important  to  instruct  mothers  that  the 
enamel  is  formed  from  cells  similar  to  those  of  the  skin  and  that  any 
eruption  or  rash  of  the  skin  is  likely  to  produce  a  deleterious  effect  upon 
the  formation  of  the  enamel,  if  it  occurs  during  the  formative  period. 

Every  precaution  should  be  taken  to  prevent  a  child  from  contracting 
measles,  chickenpox,  scarlet  fever,  etc.,  especially  from  birth  to  about 
fourteen  years  of  age  during  which  period  the  enamel  of  fifty-two  teeth 
is  formed. 

It  is  quite  common  to  see  teeth  with  an  enamel  surface  that  is  pitted 
or  grooved,  and  in  many  cases  as  much  as  half  of  the  crown  of  a  tooth 
will  be  minus  any  enamel  due  to  some  skin  disturbance  during  its 
formation.  Enamel  somewhat  similar  in  appearance  can  also  be  pro- 
duced by  any  severe  nutritional  disturbance.     It  is  practically  impos- 


298  DENTAL  PROPHYLAXIS 

sible  to  prevent  the  decay  of  this  defective  enamel,  and  any  rash  or 
eruption  should  be  avoided  for  this  reason. 

General  Comments, — One  prophylactic  treatment  does  not  con- 
stitute prophylaxis.  It  is  only  by  a  systematic,  continuous  course  of 
treatment  and  home  care  of  the  mouth  that  ideal  health  conditions 
can  be  secured. 

Preventive  dentistry  can  be  had  quite  cheaply  and  is  within  the 
reach,  financially,  of  nearly  everybody.  Good  operative  dentistry  is 
expensive  and  always  will  be,  as  is  surgery  or  the  services  of  any 
educated  and  skilful  specialist. 

Education  and  prevention  is  the  only  hope  of  solving  the  dental 
problems  for  the  masses  and  as  time  goes  on  this  service  will  be  found  as 
necessary  a  form  of  insurance  for  health  as  life  insurance  is  for  the 
protection  of  those  left  after  one  dies. 

When  the  public  really  becomes  educated  to  the  fact  that  for  the 
expenditure  ot  a  very  moderate  sum  of  money  and  a  little  energy  on  its 
part,  the  teeth  may  be  retained  throughout  life  quite  free  from  pain  and 
disease,  there  will  be  a  great  demand  for  this  form  of  service.  Every 
mouth  would  be  greatly  benefited  if  prophylactic  treatments  could  be 
administered  every  two  months.  Many  mouths  require  monthly 
treatments,  especially  those  of  children  and  adults  who  are  susceptible 
to  caries. 

In  the  search  for  some  easy  sob^tion  of  the  problem  of  dental  decay 
many  ideas  are  advanced  for  its  ultimate  control,  and  it  is  expected 
that  a  simple  method  of  doing  away  with  this  great  disease-producing 
disorder  will  be  found.  There  may  come  a  time  when  a  lozenge  will 
produce  immunity  but  that  time  is  not  in  sight  as  yet.  As  long  as 
people  live  artificially,  as  most  people  do,  eating  the  various  concoc- 
tions called  ''food"  that  they  feel  free  to  eat  at  the  present  time,  the 
one  hope  of  escape  from  the  ill-effects  of  dental  decay  and  its  attending 
serious  effects  on  the  body  is  through  the  present  knowledge  of  extreme 
cleanliness,  or  mouth  hygiene.  Until  something  can  be  presented  more 
definitely  simple  that  will  show  equally  beneficial  results,  it  will  be 
necessary  to  adhere  to  the  form  of  prophylaxis  herein  advocated. 


APPENDIX. 

THE  BROAD  FIELD  OF  SERVICE  OF  THE  DENTAL  HYGIENIST. 

The  educational  and  preventive  service  of  the  dental  hygienist  has 
been  covered  in  detail  under  Dental  Prophylaxis,  and  it  remains  to 
state  the  broad  field  to  which  such  service  may  be  applied. 

It  has  long  been  realized  that  the  dental  profession  was  unable  to 
cope  with  the  universal  need  for  mouth  hygiene,  the  number  of  dentists 
available  at  any  one  time  being  always  insufficient  to  supply  even  the 
need  for  good  operative  dentistry.  With  dental  diseases  and  resultant 
systemic  infections  almost  universal  maladies,  trained  workers  for 
maintaining  mouth 'health  can  no  longer  be  denied  to  a  public  sorely 
in  need  of  such  service.  The  dental  hygienist  was  created  from  the 
realization  that  mouth  hygiene  was  a  necessity,  that  the  average  dental 
practitioner  could  not  give  the  necessary  time  to  it,  and  that  the  tooth 
brush  alone  would  never  produce  it. 

Fortunately  it  does  not  require  a  graduate  dentist  to  perform  a 
prophylactic  treatment  of  the  teeth  or  to  teach  mouth  brushing,  food 
habits,  and  general  hygiene.  The  present  need  of  the  dental  profession, 
in  solving  the  public  health  problem  of  mouth  hygiene,  is  an  immense 
corps  of  women  workers,  educated  and  trained  as  dental  hygienists, 
and  therefore  competent  to  enter  dental  offices,  infirmaries,  public 
clinics,  sanatoriums,  factories  and  other  private  corporations,  to  care  for 
the  mouths  of  the  millions  of  adults  who  need  this  educational  service 
so  urgently.  The  need  in  every  state  is  so  great  that  every  state  must 
provide  its  own  training  schools,  and  if  the  dental  profession  will  not 
meet  the  situation,  the  state  health  or  educational  authorities  must  do 
it.  This  is  the  only  sane  and  logical  method  by  which  any  help  can  be 
provided  for  the  adult  population,  with  the  almost  hopeless  mouth 
conditions  which  now  prevail.  The  damage  has  already  been  done 
and  there  are  not  enough  dentists  to  restore  the  lost  tooth  structure  in 
one-fifth  of  these  mouths.  There  is,  however,  a  service  that  the  dental 
hygienist  can  give  in  correcting  the  uncleanliness  and  in  educating  for 
the  prevention  of  further  disease.  ~~ 


THE  DENTAL  HYGIENIST  IN  PRIVATE  PRACTICE. 

The  service  of  the  dental  hygienist  in  the  private  offices  of  graduate 
dentists  is  quite  apparent,  and  much  of  the  detail  given  under  Dental 
Prophylaxis  applied  directly  to  this  particular  field  of  service.    The 


300  .       APPENDIX 

following  system  is  offered  as  one  that  has  been  found  to  be  practical 
and  productive  of  splendid  results. 

A  System  for  Prophylaxis  in  Private  Dental  Practice. — First,  a  new 
patient  is  given  two  appointments,  a  week  or  ten  days  apart,  with  the 
dental  hygienist,  for  a  thorough  instrumentation  and  polishing  of  the 
teeth.  At  the  end  of  the  first  sitting  he  is  supplied  with  a  tooth  brush, 
dentifrice,  floss  silk  and  lime-water  for  a  mouth  wash,  taken  to  a  wash 
bowl  and  taught  how  to  properly  brush  teeth  and  gums,  and  given  full 
instructions  in  the  home  care  of  the  mouths  As  it  is  now  realized  that 
a  visual  examination  of  the  mouth  is  very  superficial  an  appointment 
is  reserved  for  the  radiographing  of  the  entire  mouth.  At  the  end  of 
the  second  sitting,  one-half  hour  is  reserved  for  him  with  the  dentist 
for  a  thorough  chart  examination  of  the  mouth  and  diagnosis  of  the 
radiographs.  Appointments  are  then  arranged,  surgical  instrumenta- 
tion given  if  necessary,  and  the  teeth  restored  to  a  sound  condition. 
At  the  end  of  the  last  appointment  the  dentist  gives  the  patient  another 
thorough  prophylactic  treatment. 

The  patient  is  then  put  on  a  list  and  sent  for  each  month  for  a  treat- 
ment by  the  dental  hygienist.  At  the  end  of  six  months  he  again  goes 
into  the  hands  of  the  dentist  for  an  examination  of  the  teeth  and  gums 
and  a  surgical  instrumentation  if  necessary.'  If  the  condition  of  his 
mouth  warrants,  the  interval  between  the  treatments  is  now  lengthened 
to  six  weeks.  At  the  end  of  the  next,  six  months  he  again  goes  through  the 
dentist's  hands  and  if  good  moutlf  health  is  attained  his  name  is  placed 
on  a  two  months'  list  and  he  is  given  treatments  by  the  dental  hygienist 
at  these  intervals,  going  into  the  dentist's  hand  for  every  third  treat- 
ment, or  once  in  six  months.  Patients  whose  teeth  are  very  susceptible 
to  dental  caries,  such  as  children  and  young  people,  should  be  retained 
on  the  monthly  or  six  weeks'  list. 

When  the  patient's  mouth  has  been  put  in  order  and  his  name  placed 
on  one  of  the  lists  to  be  sent  for  at  regular  intervals,  his  name  is  also 
entered  in  the  appointment  book  against  the  date  when  his  next 
appointment  for  a  prophylactic  treatment  falls  due.  A  week  previous 
to  this  date  the  patient  is  notified  of  the  appointment  by  means  of  a 
return  card  system.  This  consists  of  an  appointment  card  bearing  the 
name  of  the  patient  and  date  and  hour  of  his  appointment,  a  retu'rn 
card  bearing  the  same  date,  and  a  stamped  return  envelope.  If  the 
date  designated  proves  convenient,  the  patient  signs  the  return  card 
and  returns  it  in  the  enclosed  envelope  and  the  appointment  is  checked 
in  the  appointment  book.  If  not  convenient,  a  new  appointment  is 
made.  The  various  lists  of  patients — monthly,  six  weeks,  and  two 
months — are  kept  by  means  of  a  card  index  file.  In  the  writer's 
practice  this  system  has  been  compulsory,  and  has  shown  very  favorable 
results  in  the  prevention  of  dental  caries  and  pyorrhea  alveolaris.  It 
may  also  be  mentioned  that  the  system  has  proved  to  be  a  financial 
saving  of  60  per  cent,  to  the  patients. 


MUNICIPAL  DENTAL  CLINICS  301 

HOSPITALS  AND  SANATORIUMS. 

The  relation  of  pathological  mouth  conditions  to  systemic  diseases  is 
now  so  definitely  known,  that  hospitals  and  sanatoriums  will  bie  forced 
to  establish  a  dental  division  for  the  radiographing,  diagnosing,  and 
sanitation  of  the  mouths  of  all  patients.  The  sanitation  of  the  mouth 
will  necessitate  the  services  of  dental  hygienists  who  can  operate  at  the 
bedside,  if  necessary.  Such  a  procedure  is  already  being  followed  in 
some  hospitals  and  sanatoriums  with  most  gratifying  results. 

INDUSTRIAL  DENTAL  CLINICS. 

One  of  the  most  important  branches  of  dental  hygiene  is  that  which 
may  be  provided  for  the  great  working  classes  who  need  sound  teeth 
for  good  health,  but  for  whom,  until  the  present  time,  there  has  been 
no  provision  in  dentistry.  These  are  the  people  who  constantly  suffer 
from  systemic  disturbances  due  to  diseased  teeth,  yet  scientific  dental 
operations  are  out  of  their  reach.  Fortunately  preventive  dentistry  and 
education  for  mouth  health  can  be  placed  within  the  reach  of  all.  The 
economic  value  of  educational,  preventive  and  diagnostic  dental  clinics 
in  connection  with  large  industries  has  been  shown  to  be  the  most 
fruitful  form  of  welfare  work  for  employees. 

A  working  plan  for  the  industrial  clinic  is  suggested  as  follows :  The 
size  of  the  corps  is  dependent  upo:^^  the  number  of  employees  in  the 
industry..  A  unit  for  one  thousand  employees  should  include  one 
dentist,  two  dental  hygienists  and  a  radiographer.  The  service  is 
limited  to  prophylactic  treatments,  instructions  in  the  home  care  of 
the  mouth,  visual  and  radiographic  chart  examinations  of  the  entire 
mouth,  and  the  relief  of  pain.  When  the  condition  of  the  mouth  is 
charted,  a  copy  is  given  the  patient,  and  he  is  advised  to  visit  his  own 
dentist  for  the  elimination  of  mouth  infection  and  for  restoration  of  lost 
tooth  structure. 

The  serious  illnesses  of  many  valuable  employees  could  thus  be  pre- 
vented, and  industries  would  find  such  a  welfare  clinic  a  very  profitable 
investment. 

MUNICIPAL  DENTAL  CLINICS. 

High  grade  professional  service,  whether  it  be  medicine,  dentistry 
or  law,  must  be  considered  as  a  luxury  to  the  great  mass  of  wage-earning 
people  in  cities,  and  one  which  they  cannot  afford.  This  is  especially 
true  of  good  dentistry.  Cheap  dentistry  is  apt  to  be  more  harmful 
than  beneficial,  for  if  the  operations  on  the  teeth  are  performed  hastily 
and  in  an  unscientific  manner,  serious  complications  may  develop 
within  the  body,  due  to  bacteria  gaining  entrance  through  the  roots  of 
the  teeth  or  through  the  soft  tissues  which  surround  them. 

There  are  hundreds  of  families  in  cities  whose  income  is  not  suf- 
ficiently large  to  aft'ord  the  services  of  a  good  dentist  and  ^^t  they 


302  APPENDIX 

would  like  to  save  their  teeth  if  possible.  Decayed  and  diseased  teeth 
produce  much  sickness  and  lower  the  efficiency  and  endurance  of  the 
workers.  This  becomes  a  serious  health  problem  and  must  be  met  in 
a  practical  manner.  Charity,  which  gives  something  of  value  for 
nothing,  is  not  conducive  to  character  building  or  good  citizenship,  and 
he  who  accepts  it  should  be  in  desperate  need  of  aid. 

When  the  administrators  of  municipalities  realize  these  facts  they 
will  establish  municipal  dental  clinics  accessible  to  the  wage-earner 
and  his  family,  especially  the  children.  It  would  not  be  the  intention 
of  such  a  clinic  to  give  free  dental  service,  except  for  the  relief  of  pain 
to  those  who  are  too  poor  to  pay  for  it,  but  to  establish  a  clinic  where 
first-class  dentistry  might  be  secured  at  a  very  moderate  cost  and  be 
within  the  means  of  all  whose  incomes  are  too  small  to  enable  them  to 
go  or  to  send  their  children  to  a  dentist  in  private  practice,  a  movement 
to  help  those  who  are  willing  and  anxious  to  help  themselves. 
^  The  dental  hygienist  has  her  field  of  service  in  this  type  of  relief 
and  repair  clinic,  where  she  may  restore  unsanitary  mouths  to  a  clean 
and  wholesome  state  by  operative  procedure  as  well  as  education  in 
home  care. 

EDUCATIONAL  AND  PREVENTIVE  DENTAL  CLINICS  FOR 
SCHOOL  CHILDREN. 

The  efiiciency  of  dental  hygieniits  in  carrying  out  educational  and 
preventive  measures  as  a  part  of  the  scKool  curriculum  has  been 
demonstrated  for  six  years  in  Bridgeport,  Connecticut,  and  it  is  felt 
that  the  results  secured  would  be  of  sufiicient  interest  to  warrant  the 
following  detailed  report  of  this  work. 

I 
REPORT  OF  FIVE  YEARS  OF  MOUTH  HYGIENE  IN  THE    PUBLIC 
SCHOOLS  OF  BRIDGEPORT,  CONN.^ 

By  Alfred  C.  Fones,  D.D.S. 

In  presenting  a  report  of  the  findings  of  a  five-year  demonstration  of 
an  educational  and  preventive  dental  clinic  in  the  first  five  grades  of  the 
public  schools  of  Bridgeport,  Conn.,  it  is  interesting  to  review  the 
reasoning  and  deductions  by  which  the  plan  was  perfected.  Previous 
to  the  establishment  of  the  clinic  in  1914,  a  paper  entitled  "A  Plan 
that  Solves  the  Fundamental  Problem  in  School  Hygiene,"  was  read 
by  Dr.  Alfred  C.  Fones,  of  Bridgeport,  Conn.,  before  the  Fourth 
International  Congress  on  School  Hygiene,  in  Buffalo,  August  26, 
1913.  In  it  the  author  summed  up  in  a  short  article  the  physical 
status  of  the  average  school  child  and  the  problem  of  the  unsanitary 
condition  of  his  mouth,  and  evolved  a  plan  for  its  solution.     At  that 

1  Read  before  the  Convention  of  the  Connecticut  Dental  Hygienists'  Association, 
Bridgeport,  Conn.,  May^24,  1919. 


MOUTH  HYGIENE  IN  PUBLIC  SCHOOLS  303 

period  little  was  known  of  focal  infections,  which  have  proved  to  be 
a  greater  evil  than  anything  yet  recognized  as  traceable  to  decayed 
teeth.  The  paper  makes  a  logical  introduction  to  this  report  and  is 
presented  in  full  as  follows: 

Dr.  Fones'  Plan  Proposed  in  1914. — "To  analyze  the  subject  of 
hygiene  for  the  upliit  and  betterment  of  the  children  in  our  public 
schools,  we  must  determine  what  are  the  main  factors  existing  at 
present  that  act  as  a  detriment  to  proper  development  and  also  as  the 
chief  cause  of  illness  in  child  life. 

"  The  large  number  of  papers  presented  at  this  congress,  covering  so 
many  phases  of  the  subject,  merely  proves  that  we  must  reach  a  con- 
clusion, first  as  to  where  we  should  concentrate  our  energy,  and  then 
one  step  at  a  time  eliminate  the  most  conspicuous  evils  that  beset  the 
school  children  of  our  country. 

"If  our  large  steel  plants  and  rolling  mills  were  obliged  to  reroll  from 
twenty  to  thirty-five  per  cent,  of  their  stock,  it  would  not  take  them 
very  long  to  find  out  what  was  the  matter.  No  business  nowadays 
could  stand  such  a  high  percentage  of  loss  in  doing  its  work  over  again. 

"  In  our  public  schools  throughout  the  country  it  is  a  fair  estimate 
to  say  that  the  percentage  of  grammar  school  children  who  are  review- 
ing their  grades  will  range  between  twenty  and  thirty-five  per  cent.  In 
a  majority  of  the  cities  the  average  would  be  nearer  the  latter  figure. 
What  is  the  matter?  Is  it  our  system  of  teaching,  crowded  schools, 
poorly  lighted  or  ill-ventilated  buildj^ngs,  or  is  the  chief  cause  to  be 
found  in  the  material  itself — the  child  ? 

"Let  us  examine  the  average  boy  of  ten  years  of  age  and  see  what 
we  find.  Face,  ears  and  nose  unclean,  hair  unkempt,  hands  grimy  and 
finger-nails  dirty.  Shoes  splashed  with  dry  or  wet  mud,  clothes  soiled, 
and  an  odor  percolating  through  the  atmosphere  to  excite  suspicion 
that  his  little  body  has  not  been  washed  for  some  time.  His  eyesight 
may  be  good  and  yet  it  may  be  defective.  If  his  face  is  washed  it  may 
disclose  a  color  that  is  lacking  in  the  bloom  that  a  boy  of  ten  should 
have. 

"  If  otherwise  his  body  appears  normal  we  ask  him  to  open  his  mouth. 
If  his  external  appearance  troubles  us,  his  internal  appearance  would 
shock  us.  Here  we  find  teeth  covered  with  green  stain;  temporary  and 
permanent  teeth  badly  decayed,  possibly  fistulae  on  the  gum  surface 
showing  outlets  for  pus  from  an  abscessed  tooth  or  teeth,  and  decom- 
posing food  around  and  between  the  teeth.  Why  examine  the  child 
any  further  ?  Here  at  the  gateway  of  the  system  is  a  source  of  infection 
and  poison  that  would  contaminate  every  mouthful  of  food  taken  into 
his  body.  With  decomposition  instead  of  digestion  taking  place  in  the 
alimentary  tract,  it  is  no  wonder  that  the  child  suft'ers  from  an  auto- 
intoxication which  produces  eye-strain,  anemia,  malaise,  constipation,  / 
headaches,  fevers  and  many  other  ailments. 

"Such  a  mouth  is  an  ideal  breeding  ground  for  germ  life,  and  a 
child  with  such  a  mouth  is  far  more  susceptible  to  infectious  diseases 


304  APPENDIX 

than  one  whose  teeth  are  sound  and  kept  free  from  food  debris.  Sup- 
pose at  the  entrance  of  our  cities  such  a  rank  condition  existed.  How 
long  would  it  be  before  disease  and  sickness  would  be  swept  in  among 
the  inhabitants?  This  boy  described  is  but  duplicated  in  the  girl  of 
ten.  Decayed  teeth  constitute  the  most  prevalent  disease  known.  It 
is  difficult  to  find  two  children  out  of  one  hundred  with  perfectly  sound 
sets  of  teeth.  In  a  thorough  dental  examination  of  five  hundred  and 
fifty  school  children  in  the  town  of  Stratford,  Connecticut,  but  one  child 
was  found  to  have  a  set  of  teeth  free  from  decay. 

"  Look  over  the  reports  of  the  medical  inspectors  in  the  public  schools 
who  have  made  but  a  glancing  examination  of  the  mouths,  and  you  will 
find  that  decayed  teeth  outrank  all  other  physical  defects  combined. 

"  Therefore  we  must  deduce  from  our  analysis  of  school  hygiene  that 
the  most  conspicuous  defect  of  the  child  is  the  unsanitary  condition  of 
his  mouth.  Like  a  pig  pen  or  garbage  drain,  slowly  seeping  its  poison 
into  the  brook,  which,  flowing  into  the  reservoir,  contaminates  the  water 
supply  to  a  city,  so  do  the  products  of  abscessed  and  decayed  teeth  with 
decomposing  food  slowly  but  surely  poison  the  human  system.  Such 
mouths  and  teeth  breed  disease.  Such  children  cough  and  sneeze 
millions  of  germs  made  virulent  and  active  in  an  ideal  feeding  ground. 
And  then  again  the  teeth  as  a  crushing  and  masticating  machine  are  fre- 
quently ruined  by  the  time  the  child  has  reached  twelve  or  fourteen 
years  of  age.  It  is  true  that  they  can  limp  through  life  with  this  dread- 
ful handicap,  the  same  as  an  autojnobile  can  climb  a  steep  hill  on  three 
cylinders,  but  you  can  rest  assured  that  the  child  with  a  wrecked  mouth 
at  fourteen  is  traveling  on  his  second  speed  until  he  reaches  thirty-five, 
and  from  there  he  drops  into  his  low  gear  to  finish  the  journey  in  a 
slow  and  uncertain  state.  It  is  true  that  many  have  lived  to  a  ripe  old 
age  with  unclean  mouths  and  wrecked  teeth,  not  on  account  of  such 
conditions,  but  in  spite  of  them. 

"If  it  be  conceded  that  the  most  unhygienic  feature  of  child  life  is 
its  mouth  we  then  come  to  the  problem — how  can  we  establish  clean 
mouths,  sound  teeth  and  the  tooth-brush  habit?  To  try  and  fill  the  teeth 
of  the  children  in  our  public  schools  is  a  noble  charity,  but  an  endless 
chain.  Like  an  immense  flood,  decayed  teeth  have  spread  over  the  civ- 
ilized world  to  such  an  extent  that  hardly  one- tenth  of  the  population 
of  a  country  such  as  ours  could  find  a  sufficient  number  of  dentists  to 
fill  its  teeth.  I  believe  it  to  be  a  conservative  estimate  to  say  that  the 
children  found  in  the  first  five  grades  in  our  public  schools  would  aver- 
age not  less  than  six^  good-sized  cavities  in  their  teeth.  If  you  will 
but  figure  out  how  many  children  there  are  in  your  city  in  the  first  five 
grades,  you  can  roughly  estimate  the  immense  amount  of  work  there 
would  be  for  a  corps  of  dentists  to  cope  with  such  a  task  as  filling 
their  teeth.  This  would  not  mean  merely  plugging  a  hole  in  a  piece  of 
ivory;  it  means  the  painstaking  work  of  a  dental  operation  on  live  tissue. 

1  Later  findings  showecJ  seven — plus. 


MOUTH  HYGIENE  IN  PUBLIC  SCHOOLS  305 

"But  let  us  assume  that  it  is  possible  to  fill  these  teeth  and  save  them 
for  the  time  being,  how  are  we  to  prevent  a  re-occurrenee  of  decay  as 
well  as  to  check  the  flood  with  the  children  coming  into  the  schools  in 
the  primary  grades  each  year?  Surely  every  dentist  knows  that  the 
tooth  brush  alone  will  not  stop  it,  and  every  dentist  also  knows,  as  well 
as  the  parent,  how  difficult  it  is  to  induce  children  to  properly  brush 
their  teeth  and  take  care  of  their  mouths  as  they  should.  Would  it  not 
be  better  to  evolve  a  system  for  the  prevention  of  dental  decay  and  the 
establishment  of  clean  mouths  than  try  to  cope  with  the  hopeless  task  of 
filling  the  thousands  of  decayed  teeth?  I  am  heartily  in  sNiiipathy 
with  the  scheme  that  every  city  should  have  a  dental  clinic  for  the  school 
children  for  the  relief  of  pain,  and  I  believe  it  is  inhuman  in  this 
twentieth  century  to  allow  the  poorer  class  of  children  to  suffer  as  they 
do  from  toothache.  But  let  us  draw  a  line  on  the  conditions  as  they 
exist  today,  and  I  would  present  this  plan,  partly  suggested  by  Dr. 
Ottolengui,  of  New  York,  for  your  consideration. 

"It  is  a  clinical  fact  that  fully  eighty  per  cent,  of  dental  decay  can 
be  prevented,  if  monthly  or  even  bi-monthly  surface  polishing  of  the 
teeth  with  orange  wood  sticks  and  fine  pumice  can  be  systematically 
followed.  These  treatments,  of  course,  to  be  augmented  by  the  faithful 
and  correct  use  of  the  tooth  brush,  floss  silk  and  lime-water  as  a  moi^th 
wash. 

"Suppose  it  were  possible  to  start  a  year  from  this  September  and 
place  in  our  schools  trained  women  who  would  confine  their  efforts  the 
first  year  to  the  children  in  the  first  grade.  These  w^omen  to  be  trained 
and  educated  as  hygienists  who  would  be  competent  to  give  each  child 
a  surface  treatment  of  the  teeth  once  a  month ;  each  woman  to  have  the 
supervision,  to  start  with,  of  two  hundred  children;  these  children  in 
the  first  grade  to  be  taught  the  proper  use  of  the  tooth  brush,  mouths 
inspected  daily  for  cleanliness,  and  no  child  permitted  to  enter  the  class 
room  who  had  not  brushed  his  teeth.  Hands  and  face  to  be  clean 
and  hair  combed.  Bodily  cleanliness  also  insisted  upon  and  efforts 
made  to  secure  the  cooperation  of  the  parents.  Talks  in  the  class  room 
as  well  as  the  use  of  the  stereopticon  in  the  assembly  room  would  greatly 
aid  in  securing  the  desired  results.  These  hygienists  could  also  be  of 
great  aid  to  the  medical  inspectors.  At  the  end  of  the  year  they  would 
follow  the  children  into  the  second  grade  and  a  new  corps  of  hygienists 
would  enter  the  first  grade  with  the  new  pupils;  this  to  be  repeated  for 
five  years,  until  the  first  corps  of  women  were  caring  for  their  children 
in  the  fifth  grade.  It  is  doubtful  if  it  would  be  necessary  to  carry  this 
work  beyond  th,e  fifth  grade,  as  the  child  would  be  cared  for  through 
the  most  susceptible  period  for  dental  decay. 

"Now  what  would  such  a  system  mean  to  the  children?  It  would 
m§an  that  from  the  first  day  that  the  child  entered  school  it  would  be 
taught  cleanliness.  That  when  the  first  permanent  tooth  entered  the 
mouth  it  woukl  be  under  the  supervision  of  the  hygienist,  who  would 
teach  the  child  how  to  keep  it  clean  and  who  would  also  aid  with  the 
20 


306  APPENDIX 

monthly  polishing.  It  would  mean  that  during  the  first  five  years  of 
school  life  habits  of  cleanliness  would  be  established  that  would  mold 
these  boys  and  girls  into  new  types  of  men  and  women.  Fully  three- 
quarters  of  the  diseases  incident  to  child  life  would  be  eliminated.  With 
an  additional  knowledge  of  food  values  and  how  to  properly  masticate 
their  food  instead  of  bolting  it,  the  main  factors  for  hygiene  would 
be  covered. 

"  Booker  Washington  once  said :  '  If  I  can  teach  the  colored  man  the 
gospel  of  the  tooth  brush,  I  feel  that  I  can  make  a  man  of  him.'  Those 
of  you  who  see  but  little  of  children  can  hardly  realize  what  an  uplift 
and  different  point  of  view  there  comes  with  a  clean  mouth  and  pol- 
ished teeth.  It  is  interesting  to  see  a  child  whose  teeth  have  been  pol- 
ished and  a  washbowl  instruction  given  in  the  use  of  the  tooth  brush, 
gradually  change  in  general  appearance  regarding  cleanliness.  I  have 
known  them  in  a  few  weeks  to  choose  a  new  set  of  companions  because 
the  old  friends  no  longer  looked  attractive  to  them.  No  one  ever  saw 
a  rowdy  with  a  clean  mouth,  for  cleanliness  breeds  refinement.  The 
proper  food  supply  to  the  body  and  cleanliness  are  the  two  main  founda- 
tion pillars  for  health,  and  these  must  be  taught  and  practised  before 
we  can  hope  to  obtain  satisfying  results  in  the  betterment  of  child  life. 
There  is  much  in  life  worth  while  besides  teeth,  but  I  know  of  no  one 
factor  that  is  more  conducive  to  health  than  sound  teeth  and  a  clean 
mouth.  ^ 

"  The  question  may  be  asked :  How  are  we  to  educate  these  women  to 
be  dental  hygienists?  In  every  large  city  there  are  men  in  both  the 
medical  and  dental  professions  who  are  competent  to  establish  a  lecture 
course  for  this  purpose.  The  necessary  training  in  the  prophylactic 
treatment  of  the  teeth  would,  of  course,  be  given  by  dentists.  Both  of 
these  professions  are  anxious  to  aid  in  any  cause  so  worthy,  and  I  believe 
they  would  willingly  give  their  time  and  knowledge  to  start  such  a 
movement.  It  is  impossible  in  this  paper  to  give  the  details  concerning 
the  education  of  these  women  and  their  full  duties  in  the  schools,  but 
enough  has  been  stated  to  permit  those  in  charge  of  our  public  school 
systems  to  consider  the  proposition  in  a  general  way  and  determine  if 
this  plan  is  a  solution  of  the  main  problem  regarding  school  hygiene." 

Inception  of  the  Bridgeport  Experiment. — For  four  years  previous  to 
1913,  strenuous  efforts  had  been  made  to  interest  the  city  officials  of 
Bridgeport  to  provide  funds  for  an  educational  and  preventive  dental 
clinic  in  the  public  schools.  At  last  five  thousand  dollars  was  appor- 
tioned to  the  Board  of  Health  in  order  that  a  demonstration  might  be 
made  to  prove  the  value  of  a  mouth  hygiene  campaign  conducted  on  an 
educational  and  preventive  plan. 

With  the  possibility  of  this  movement  being  a  powerful  aid  in  the 
prevention  of  dental  decay,  infectious  and  communicable  diseases, 
eighteen  prominent  educators  in  the  East  agreed  to  come  to  Bridgeport 
and  give  their  services  gratis  to  educate  a  corps  of  women  to  be  known 


^&AJUvy^6MsA  C^      Ui^^\ 


MOUTH  HYGIENE  IN  PUBLIC  SCHOOLS  307 

as  dental  hygienists.     The  course  was  started  in  the  late  fall  of  1913, 
and  in  June,  1914,  the  first  class  of  dental  hygienists  was  graduated. 

Tfie'B^oardof  Health  appointed  a  committee  of  four  dentists  and  one 
member  of  the  Health  Board,  a  physician,  to  estaV^lish  the  system  in 
the  schools.  Eight  dental  hygienists  and  two  supervisors  were  chosen, 
and  in  vSeptember,  1914,  the  work  was  begun  for  the  first  and  second 
grade  children. 

First  Hygienists  at  Work  in  Public  Schools. — There  were  four  distinct 
parts  to  the  system.  First,  the  prophylactic  treatment  or  the  actual 
cleaiiing  and  polishing  of  the  children's  teeth  and  chart  examination  of 
the  mouths.  Second,  tooth-brush  drills  and  class-room  talks.  Third, 
stereopticon  lectures  for  children  in  the  higher  grades;  and,  fourth, 
educational  work  in  the  homes  by  means  of  special  literature  for 
parents.  The  prophylactic  treatment  consisted  mainly  in  the  thorough 
cleaning,  by  means  of  orange  wood  sticks  in  hand  polishers,  of  every 
surface  of  every  tooth.  This  meant  that  the  dental  hygienist  would 
remove  all  stains  and  accretions  from  the  surfaces  of  the  teeth,  and 
especially  the  mucilaginous  films  known  as  bacterial  plaques,  which 
are  the  initial  step  of  dental  decay.  The  treatments  were  given  in  the 
schools,  the  equipment  being  portable  and  adapted  to  almost  any 
location.  Every  child  received  the  same  treatment,  regardless  oi  the 
financial  status  of  the  parent;  in  short,  this  preventive  system  was 
incorporated  as  part  of  the  school  f  ^.rriculum.  Some  parents  objected, 
thinking  the  work  was  a  charity,  fmt  with  a  better  understanding  of  it 
the  objections  were  soon  withdrawn. 

The  tooth-brush  drills  were  given  by  the  supervisors,  and  a  method 
of  mouth  brushing  was  taught  for  use  in  the  home.  No  attempt  was 
made  to  use  water  and  a  dentifrice  in  the  class  room,  as  this  would  prove 
to  be  too  mussy.  Class-room  talks  concerning  foods,  cleanliness,  etc., 
were  part  of  the  drill.  The  total  number  of  children  examined  and 
treated  in  the  first  and  second  grades  the  first  year  was  6768.  On  the 
first  examination  less  than  ten  per  cent,  were  brushing  their  teeth  daily. 
About  thirty  per  cent,  claimed  that  they  brushed  their  teeth  occasion- 
ally, while  sixty  per  cent,  were  frank  enough  to  state  that  they  did  not 
use  a  tooth  brush.  Ten  per  cent,  of  the  children  were  found  to  have 
fistulse  on  the  gums,  showing  the  outlets  of  abscesses  from  the  roots  of 
decayed  teeth,  and  they  averaged  over  seven  cavities  per  child.  It  was 
shocking  to  find  the  mouths  of  these  children  ranging  from  five  to  seven 
years  in  this  deplorable  condition,  and  it  was  appalling  to  contemplate 
the  conditions  that  would  exist  in  these  mouths  as  the  children  grew  up. 
It  presented  very  interesting  material  to  work  with. 

It  will  take  a  long  period  of  public  education  before  the  mouths  of 
the  incoming  children  to  our  first  grade  will  show  any  great  degree  of 
improvement.  From  birth  to  five  or  six  years  of  age  they  are  entirely 
under  the  home  influence  and  are  permitted  to  eat  foods,  especially 
sweets,  that  are  conducive  to  decay,  and  mouth  cleanliness  is  not  com- 
pulsory.    Slowly  but  surely  the  public  school  education  will  seep  back 


308  APPENDIX 

into  the  homes,  and  with  the  aid  of  the  older  children  and  pamphlets 
it  is  our  hope  that  eventually  the  mouths  of  these  children  will  present 
a  much  improved  condition. 

Corps  of  Hygienists  Increased.  In  September,  1915,  six  additional 
hygienists  were  added  to  the  corps  to  advance  the  work  to  cover  the 
first  three  grades.  This  gave  a  sufficient  number  of  workers  until 
1917  when  six  more  were  added,  so  that  this  care  could  be  given  to  all 
the  children  in  the  first  five  grades,  numbering  about  15,000. 

In  January,  1918,  the  parochial  schools  petitioned  the  Board  of 
Health  and  also  the  Board  of  Apportionment  to  have  this  system 
extended  to  them  as  a  health  measure.  This  petition  was  granted  and 
in  September  six  more  hygienists  were  added  to  the  corps  for  this 
purpose,  making  twenty-six  in  all.  At  the  present  time  these  women 
have  under  their  care  the  mouths  of  nearly  twenty  thousand  children 
in  the  first  five  grades. 

We  have  also  employed  three  women  dentists,  who  are  filling  the 
small  cavities  in  the  first  permanent  molars  for  the  children  in  the  first 
and  second  grades.  Many  of  these  children,  on  entering  school,  have 
small  cavities  developing  in  these  most  important  teeth,  and  in  order 
that  all  the  children  may  start  on  an  equal  basis  in  the  future  preven- 
tion of  dental  decay  of  the  permanent  teeth,  all  are  eligible  and  are 
encouraged  to  have  these  small  cavities  filled. 

Examination  of  Fifth  Grade  Children. — In  order  to  prove  definitely 
the  value  of  education  and  preventibn,  it  was  necessary  to  have  data 
of  the  condition  of  the  mouths  of  children  in  a  higher  grade  who  had 
never  had  the  advantage  of  prophylactic  treatments,  tooth-brush  drills, 
and  education  in  mouth  hygiene.  The  children  of  the  fifth  grade  were 
chosen  as  the  control  class,  and  this  report  will  present  the  comparison 
of  their  mouth  conditions  with  the  present  fifth  graders,  who  have  had 
prophylactic  treatments  and  education  in  mouth  hygiene  for  the  first 
five  years  of  their  school  life.  They  have  had  no  repair  work  provided 
for  them  and  the  educational  side  has  been  three-quarters  of  the  work 
of  the  dental  hygiene  corps. 

In  making  this  demonstration  it  was  not  our  expectation  to  make  a 
startling  reduction  in  the  percentage  of  dental  decay,  the  main  object 
being  to  show  up  the  pernicious  mouth  conditions  prevailing  among 
school  children  and  to  prove  the  value  of  prevention  and  education  in 
mouth  hygiene  for  great  numbers  of  children  in  preference  to  exten- 
sive repair  clinics,  with  no  effort  to  eliminate  the  source  of  the  trouble. 
It  would,  of  course,  have  been  ideal  to  have  had  the  two  types  of  clinics 
and  to  have  put  the  children's  mouths  in  sound  condition,  but  funds 
were  not  available  for  this  purpose,  and  the  excellent  report  shown  is 
merely  the  result  of  education  and  prevention. 

For  the  purpose  of  securing  this  data  a  complete  record  chart  has 
been  maintained  of  the  condition  of  every  child's  mouth  at  each  succes- 
sive treatment,  and  the  following  figures  were  obtained  by  comparing 
the  average  number  of  cavities  per  child  in  the  fifth  grade  of  a  given 


MOUTH  HYGIENE  IN  PUBLIC  SCHOOLH  309 

school  with  the  average  secured  from  the  same  grade  of  the  same  school 
several  years  ago.  The  demonstration  was  conducted  in  thirty  schools 
and  this  year  twenty  thousand  individual  children  received  this  treat- 
ment and  education. 

Dental  Caries. — Following  is  the  percentage  of  reduction  of  cavities 
in  the  permanent  teeth  of  the  fifth  graders  in  these  schools: 

The  highest  was  Barnum  school,  which  showed  a  reduction  of  67.5 
per  cent.  ' 

The  following  five  schools  were  over  57  per  cent. :  Huntington  Road, 
Kossuth,  Prospect,  Grand  and  Sheridan. 

Two  schools,  Maplewood  and  Franklin,  showed  over  a  50  per  jent. 
reduction. 

Three  schools,  Summerfield,  Lincoln  and  Staples,  were  over  40 
per  cent. 

Washington,  Wheeler  and  Black  Rock  were  over  30  per  cent, 

Newfield,  Garfield,  Hall,  Jackson  and  Shelton  were  over  25  per  cent. 

Bryant,  Elias  Howe  and  Madison  were  over  20  per  cent. 

Those  over  15  per  cent,  were  Waltersville,  Jefferson,  Longfellow, 
Columbus  and  Webster. 

One  school.  Read,  was  below  10  per  cent.,  and  two  schools,  Whittier 
and  McKinley,  showed  a  minus  record. 

The  total  average  for  all  these  schools  amounts  to  33.9  per  cent.^ 

Although  the  principals  and  teachers  have  given  splendid  cooperation 
in  many  of  the  schools  that  have  l(t'^;  records,  they  had  to  contend  with 
a  certain  number  of  children  whose  home  influence  was  not  conducive 
to  any  interest  in  mouth  hygiene. 

Difficulties  Met  With.^ — The  two  schools  which  showed  a  minus  record 
were  unfortunate  enough  to  have  a  number  of  children  who  were  so 
absolutely  negligent  in  the  care  of  their  mouths  that  they  dragged  down 
what  would  have  been  a  reasonably  good  average  by  three-quarters 
of  the  children. 

Bridgeport  has  been  one  of  the  most  difficult  cities  in  which  to  carry 
on  a  demonstration  of  this  kind.  We  have  a  large  foreign  population 
of  which  many  parents  do  not  speak  English.  Being  a  munition  center 
during  the  war  period,  the  population  increased  many  thousa^nds,  over- 
crowding the  city  and  schools.  The  school  records  showed  in  the  past 
year  that  58  per  cent,  of  the  children  changed  addresses  and  that  the 
population  was  constantly  shifting.  The  principals  and  teachers  were 
occupied  with  many  war  duties,  such  as  Junior  Red  Cross,  thrift  stamps, 
Hoover  programs,  etc.  In  short,  no  period  could  have  been  more 
unpropitious  for  a  serious  demonstration  of  this  kind. 

Aside  from  this,  the  value  of  education  and  prevention  has,  with 
deliberate  intent,  been  put  to  the  hardest  possible  test.  No  effort  has 
been  made  to  address  or  educate  the  teachers  or  to  enforce  cooperation 
through  the  office  of  the  superintendent  of  schools.  The  supervisors 
and  dental  hygienists  have  been  permitted  to  win  their  own  way,  so 

/  1  Percentage  of  reduction  was  49.6  for  1919-20. 


310  APPENDIX 

that  it  might  be  demonstrated  that  what  was  accompHshed  in  Bridge- 
port could  be  accompHshed  in  any  city. 

Reduction  of  Dental  Caries. — ^We  beUeve  that  from  70  per  cent,  to 

|f80  per  cent,  of  dental  caries  can  be  eliminated  through  the  public 

school  system  by  the  incorporation  in  the  school  curriculum  of  a  definite 

'health  program,  making  hygiene  one  of  the  requisites  for  promotion. 

This  would  insure  the  cooperation  and  interest  of  the  child,  teacher 

and  parent. 

The  elimination  of  dental  decay  is  so  dependent  upon  factors  other 
than  cleanliness  and  education  in  mouth  hygiene  that  it  is  surprising  to 
note  the  large  reduction  in  many  schools.  The  most  important  factor 
is  that  ofjiiet,  and  cooperation  in  this. matter  can  be  secured  only  after 
many  years  of  education.  The  correct  feeding  of  a  child  from  birth 
to  twelve  years  would  in  itself  partially,  if  not  wholly,  eliminate  dental 
decay.  The  education  of  mothers  regarding  the  feeding  of  children 
after  they  reach  an  age  when  milk  does  not  meet  the  requirements 
of  the  body  is  very  essential,  but  it  is  necessarily  slow,  and  little 
cooperation  can  be  secured  at  this  time.  The  most  important  factor 
i^ould  be  the  elimination  of  free  sugar  from  the  diet.  This  seems  radical 
to  the  vast  majority  of  our  people  who  consume  ninety  pounds  of  sugar 
)er  capita  per  year  and  look  upon  it  as  a  food  and  a  necessary  part  of 
the  diet.  This  is  an  erroneous  idea,  since  nature  has  provided  all  the 
sugar  that  the  body  requires  in  various  common  foods,  as  milk,  fruits, 
some  of  the  vegetables,  etc.,  besid^^  providing  that  all  starchy  foods, 
such  as  potatoes,  bread,  macaroni,  rice,  etc.,  be  changed  into  sugar  in 
the  digestive  process. 

The  excessive  consumption  of  free  sugar  is  undoubtedly  the  cause 
of  exceedingly  poor  teeth  among  the  English,  French  and  American 
peoples. 

It  is  not  hard  to  imagine  that  a  very  large  percentage  of  children 
are  constantly  laboring  under  a  handicap  of  faulty  feeding  which  in 
turn  produces  a  long  line  of  other  handicaps,  such  as  malformed  jaws, 
decayed  teeth,  underdevelopment,  malnutrition,  etc.,  while  the  most 
normal  conditions  could  be  secured  by  correct  diet  and  cleanliness. 

Malocclusion. — Aside  from  deatal^decay,  the  most  noticeable  defect 

in  the  mouths  of  the  school  children  is  lack  of  proper  relationship 

between  the  jaws  and  teeth,  or  malocclusion.     The  symmetrical  devel- 

fopment  of  the  brain  case  and  the  bones  of  the  face,  as  well  as  good 

I  digestion,  is  dependent  upon  a  perfect  masticating  machine.     It  was 

^-ttstenishing  to  note  that  malocclusion  was  present  in  98  per  cent,  of  all 

the  children  examined  in  the  past  five  years.     Xhlljde/plorable^ondition 

could  be  remedied  to  a  great  degree  by  the  feeding  in  early  childhood 

of  the  Hard,  coarse  foods  requiring  pressure  to  thoroughly  masticate, 

and  by  the  prevention  of  any  pernicious  habits,  such  as  thumb  sucking, 

the  use  of  pacifiers,  mouth  breathing,  etc.     Undoubtedly  adenoids 

would  be  prevented  to  a  marked  degree  if  the  roof  of  the  mouth  could 

be  broadened  and  lowered  by  such  pressure  exerted  in  chewing.    This 


MOUTH  HYGIENE  IN  I'lJIiLIC  SCHOOLS  'M] 

would  permit  of  wide  nasal  cavities  that  would  be  conducive  to  nose 
breathing  and  proper  functioning  of  the  nasal  passages. 

When  but  two  per  cent,  of  our  school  children  have  regular  teeth  it 
adds  to  the  difficulty  of  eliminating  dental  decay,  since  irregular  teeth  /" 
offer  the  greatest  opportunity  for  the  formation  of  cavities  and  render  ^ 
the  thorough  cleansing  of  the  mouth  very  difficult. 

Retardation. — Our  modern  city  school  systems  all  have  a  smaller  or 
greater  per  cent,  of  retarded  pupils.  The  test  of  the  success  of  any  city 
school  system  at  any  given  time  is  not  whether  there  be  at  that  time 
a  large  percentage  of  retarded  children,  but  whether  a  decided  trend 
can  be  traced  toward  an  increase  or  decrease  in  percentage  of  such 
retarded  children. 

Retardation  is  a  serious  matter  from  the  standpoint  of  the  p)upil,  the 
parent,  the  teacher,  and  the  community.  Retardation  means  reeduca- 
tion, and  this  in  turn  means  the  application  of  public  funds  for  repeating 
the  operation.  In  the  figures  given  below  the  very  liberal  standard 
adopted  for  retardation  permits  the  child  to  be  two  years  older  than 
his  grade  would  warrant  and  still  be  classified  as  regular.  Those  who 
are  more  than  two  years  older  than  entering  the  first  grade  at  the  age 
of  five  would  indicate,  are  classified  as  retarded. 

The  statistics  at  hand  in  the  office  of  the  Board  of  Education  are 
not  available  year  by  year,  but  two  general  surveys  have  been  made — 
one  during  September,  1912,  and  the  other  in  November,  1918.  These 
surveys,  called  the  Age-Grade  Repf)rt,  immediately  precede  the  open- 
ing of  our  work  and  occur  near  the  close  of  the  first  five-year  periods 
and  so  offer  rather  unusual  opportunity  for  inference  as  to  the  effects 
produced.  Reduced  to  a  percentage  basis,  the  changes  that  have 
taken  place  in  the  matter  of  retarded  pupils  in  the  grammar  schools 
are  summarized  in  the  following  table : 

PERCENTAGE  OF  RETARDED  PUPILS. 

September,  1912.       November,  1918.  Drop  in 

Grade.  Per  cent.  Per  cent.  retardation. 

I 16.5  8.1  51 

II 37.0  15.3  58 

III 53.0  24.7  53 

IV 59.5  31.7  47 

V 61.0  33.1  45 

VI 54.0  30.4  44 

VII 39.0  19.3  50 

VIII 27.0  12.5  54 

Average 40.0  20.1  50 

This  reduction  of  retardation  by  50  per  cent,  is  a  really  wonderful 
change  to  be  accomplished  in  any  school  system  in  a  period  of  five  or 
six  years.  Few  people  have  realized  the  cost  in  money — ^which  is  only 
one  of  the  evils  of  retardation — of  the  reeducation  of  our  retarded 
children.     By  actual  figures  the  following  statement  holds  true: 

Cost  for  reeducation  in  Bridgeport,  1912,  equals  42  per  cent,  of  entire 
budget. 


I. 

II. 

III. 

IV. 

V. 

Sept.,  1912 

13 

17 

58 

107 

169 

Nov.,  1918 

0 

0 

11 

35 

109 

312  APPENDIX 

Costs  for  reeducation  in  Bridgeport,  1918,  equals  17  per  cent,  of 
entire  budget. 

One  has  only  to  consider  the  financial  side  to  recognize  that  any 
reduction  in  retardation  is  an  accomplishment  devoutly  to  be  sought 
through  all  legitimate  means.  Bridgeport  has  been  moving  distinctly 
forward  in  this  matter. 

That  this  change  has  been  a  vital  one  to  the  self-respect  of  the  pupils 
and  in  the  advance  of  the  moral  conditions  of  the  normal  children  is 
easily  realized  when  one  stops  to  consider  the  change  in  the  location 
in  our  grades  of  the  pupils  fourteen  years  old  and  over  that  has  come 
about  during  this  same  1912-1918  survey. 

PUPILS   FOURTEEN  YEARS    OLD   OR   OVER. 

VI.  Grades. 

212 — 4.0  per  cent,  of  elementary  pupils. 

155 — 1.5  per  cent,  of  elementary  pupils. 

Nor  does  this  tell  the  entire  story.  As  a  result  of  the  1912  survey 
the  following  statement  is  made :  "  During  the  fifteen  months  ending 
last  December,  1356  children  in  Grades  II  to  VI,  all  of  the  retarded  class, 
and  over  fourteen  years  of  age,  left  school  to  go  to  work."  Examina- 
tion of  the  records  of  the  State  Examination  Board  reveals  the  fact 
that  during  the  same  period  of  the  last  year  less  than  300  pupils,  all  ot 
whom  came  from  grades  V  and  VI,  received  working  certificates. 

Another  effective  proof  of  the^reat  forward  movement  that  has 
taken  place  in  the  lower  grammar  school  grades  is  submitted  in  the 
following  form : 

In  1912,  60  per  cent,  of  all  the  children  registered  in  the  grammar 
schools  were  below  the  fourth  grade,  while  in  1918  but  50  per  cent, 
were  below  the  fourth  grade.  Similarly,  in  1912,  85  per  cent,  were 
below  the  sixth  grade,  and  in  1918  but  78  per  cent,  were  below  the 
sixth  grade. 

Without  taking  into  consideration  the  physical  condition  of  the 
children,  educators  claim  that  the  three  major  factors  producing 
retardation  are: 

II .  Overcrowded  class  rooms. 
'p.  Uninteresting  and  unsuitable  courses  of  study. 
f  3.  Unqualified  teachers. 
"Regarding  the  first,  the  following  situation  is  interesting  to  note: 
Average  pupils  per  teacher,  1912,  38. 
Average  pupils  per  teacher,  1918,  40. 
The  cause  for  reduction  in  retardation  does  not  lie  here.     This  has 
been  rather  a  hindrance  to  its  reduction. 

In  regard  to  the  course  of  study,  a  very  effective  reorganization  of 
the  subject  matter  in  arithmetic,  geography,  language  and  history  has 
been  made  within  the  past  three  years,  and  that,  no  doubt,  has  had  a 
large  influence  in  the  matter  of  producing  an  interest  in  their  work 


MOUTH  HYGIENE  IN  PUBLIC  SCHOOLS  313 

on  the  part  of  the  pupils.  This  must  have  had  a  very  potent  influence 
in  reduction  of  retardation. 

With  respect  to  the  matter  of  teachers,  the  personnel  and  chief  source 
of  supply  in  Bridgeport  remains  about  the  same  as  in  1912.  Our  City 
Normal  School  produces  most  of  the  additional  teachers  placed  in  the 
grammar  school  grades.  A  well-arranged  study  program  has  been 
introduced  for  teachers  requiring  application  to  approved  courses  for 
advancement  in  salary,  and  this  has  probably  resulted  in  a  more  wide- 
awake teaching  body  than  we  had  in  1912. 

These  changes,  however,  could  hardly  have  effected  on  their  own 
account  the  phenomenal  reduction  in  retardation  that  has  occurred  in 
the  period  stated.  The  most  sanguine  advocate  would  hardly  take  the 
ground  that  such  a  remarkable  change  had  been  effected  simply  by 
the  introduction,  late  in  the  period  under  discussion,  of  modified  courses 
of  study.  There  must  have  been  other  contributing  factors  with  a  large 
influence. 

Our  dental  work  has  called  attention  to  the  necessity  of  taking  into 
account  the  child's  well  being.  For  the  greater  part  of  the  period  of 
this  demonstration  this  work  stood  practically  alone  in  any  progressive 
health  movement.  During  the  latter  part  it  has  been  aided  by  the  City 
Health  Department  w^th  an  enlarged  force  of  nurses,  and  at  the  present 
time  the  Superintendent  of  Public  Schools  is  planning  a  Health  Program 
to  be  introduced  into  the  grammar  schools  in  September  as  a  big,  serious 
effort  in  recognition  of  the  fundanv^ntal  physical  basis  for  all  education. 
He  says:  "The  dental  clinic  has  been  without  question  a  great  factor 
in  the  health  of  the  children,  and,  therefore,  must  have  been  one  of  the 
factors  in  reducing  the  condition  of  retardation,  which  figures  show  have 
been  reduced  50  per  cent,  since  November,  1912.  Our  promotions 
now  are  better  than  normal." 

With  all  these  facts  balanced  it  seems  only  fair  to  conclude  that  while 
the  work^of  the  Dental  Division  in  the  public  schools  is  somewhat 
intangible,  it  hasj^had  a  very  marked  effect  upon  a  more  normal  promo- 
tion of  children,  since  the  change  cannot  be  explained  by  other  factors. 

Communicable  Diseases. — The  forms  of  communicable  diseases 
where  mouth  hygiene  could  play  an  important  part  for  prevention  are 
those  which  involve  the  respiratory  tract  or  find  ingress  to  the  body 
through  the  mucous  membrane  lining  the  mouth,  throat  and  nares. 
The  resistance  to  bacterial  invasion  may  not  be  determined  entirely 
by  the  contents  of  the  blood,  but  by  the  tone  and  resistance  of  the  cells 
of  the  individual  tissues  on  which  the  bacteria  may  lodge  temporarily. 
One  bacterium  does  not  produce  a  disease.  It  is  only  when  the 
environment  proves  favorable  for  their  propagation  and  the  production 
of  large  numbers  that  infection  occurs. 

Any  continuous  effprt  that  has  for  its  object  the  removal  of  dead 
animal  and  vegetable  matter,  such  as  food  debris,  from  all  the  surfaces 
of  all  the  teeth,  the  stimulating  and  keeping  up  of  the  tone  of  the  mem- 
brane lining  the  mouth,  and  the  reducing  of  the  number  of  bacteria  in 


314  APPENDIX 

the  mouth  to  a  minimum,  must  act  as  a  powerful  preventive  by  aiding 
the  tonsils,  the  soft  palate,  and  the  pharynx  to  maintain  a  normal  and 
healthful  condition. 

Conversely,  those  mouths  which  are  neglected  and  contain  decayed 
teeth  with  decomposing  food,  red  and  congested  gums,  enlarged  tonsils 
and  a  palate  and  pharynx  covered  by  an  irritated  and  partly  congested 
mucous  membrane,  present  an  ideal  field  for  the  lodgment  and  incuba- 
tion of  the  pathogens.  How  much  of  the  communicable  diseases  that 
gain  ingress  through  the  mouth  will  finally  be  eliminated  from  child 
life  in  our  public  school  system  by  an  enforced  system  of  mouth  hygiene 
is  still  a  question,  but  all  evidence  seems  to  show  that  a  clean  mouth 
with  sound  teeth  is  the  one  most  important  factor  for  prevention. 

Up  to  a  short  time  ago  we  had  no  tangible  records  in  the  Depart- 
ment of  Health  that  pertained  to  communicable  diseases  in  the  children 
of  our  public  schools,  whereby  comparisons  could  be  made  from  year  to 
year  of  an  increase  or  decrease  in  the  numbers  of  these  diseases.  It  is, 
therefore,  impossible  at  the  present  time  to  show  what  obtained  in  the 
schools  four  or  five  years  ago  in  comparison  with  what  obtains  today. 

Out  of  the  death-rates  from  all  causes  in  this  city  we  have  been  able 
to  find  records  of  three  diseases  which  are  so  common  among  children, 
namely,  diphtheria,  measles  and  scarlet  fever.  These  are  figured  on  a 
basis  of  per  100,000  population,  and  show  the  following : 

1914.  1918. 

i   Diphtheria ^   .      .      .      .     36.6  18.7 

i  Measles 20.0  4.1 

'■'  Scarlet  fever 14.1  0.5 

From  the  death-rate  tables  the  general  inference  must  be  that  the 
percentage  of  communicable  diseases  is  gradually  decreasing. 

Influenza. — The  record  of  Bridgeport  during  the  great  scourge  of 
influenza  was  an  exceptionally  good  one.  The  deaths  amounted  to 
5.2  per  cent,  per  1000  population.  This  is  the  lowest  record  we  have 
been  able  to  find  as  yet  in  cities  approaching  the  size  of  Bridgeport. 

The  City  Health  Officer  took  the  stand  that  since  influenza  was 
spread  by  the  expelled  secretions  of  the  mouth  and  respiratory  tract, 
the  greatest  means  of  suppressing  this  disease  would  be  the  knowledge 
of  children  and  adults  of  the  dangers  of  coughing,  sneezing  and  spitting. 
He  inaugurated  an  intensive  educational  campaign  in  theaters,  motion- 
picture  houses  and  at  all  public  gatherings  regarding  the  contraction 
and  spread  of  influenza.  During  this  period  he  stated  that  an  intelli- 
gent background  for  this  education  had  been  prepared  by  the  regular 
work  of  the  dental  clinic  in  instructing  children  individually  and  in  dis- 
tributing thousands  of  hygiene  pamphlets  in  the  homes  for  the  enlightr 
enment  of  the  parents,  regarding  common  ways  of  spreading  diseases 
and  the  hygiene  of  prevention.  Five  years  of  such  education  in  con- 
junction with  mouth  hygiene,  played  an  important  part  in  giving  our 
citizens,  as  a  whole,  a  more  intelligent  impression  regarding  contagious 


MOUTH  HYGIENE  IN  l^UBIJC  SCHOOLS  3lo 

diseases,  and  the  health  officer  and  his  co-workers  had  a  more  enhght- 
ened  public  to  work  with.  He  states  further  that  "  the  most  important 
side  of  this  work  is  the  educational  opportunities  afforded  the  h ygienist. 
She  is  an  important  factor  in  raising  the  sanitary  intelligence  of  the 
community,  which  is,  after  all,  the  object  for  which  modern  health 
workers  are  striving." 

Summary. — To  summarize :  we  have  found  that  in  schools  or  districts 
where  little  or  no  attention  has  been  given  to  mouth  hygiene  it  is 
difficult  to  find  three  children  out  of  a  hundred  with  teeth  entirely  free 
from  dentaLcarieSv— We  have  also  found  that,  owing  to  this  lack  of 
e'ducatTon  and  enlightenment,  not  more  than  10  per  cent,  of  the 
children  were  using  a  tooth  brush  daily.  That  malocclusion,  which 
means  that  the  teeth  are  out  of  their  normal  position  in  the  mouth, 
thus  preventing  their  striking  the  teeth  in  opposition,  as  nature  intended 
they  should  strike,  is  as  common  as  dental  caries 


That  retardations  are  greatly  influenced  by  the  toxic  effect  pro- 
duced by  numerous  bacteria  in  unclean  mouths  and  in  diseased  and 
pulpless  teeth. 

Although  properly  tabulated  records  of  the  Board  of  Health  do  not 
date  back  far  enough  to  show  facts  and  figures  regarding  communicable 
diseases,  yet  we  have  sufficient  data  which,  on  close  observation,  con- 
vinced us  that  mouth  hygiene  is  to  be  a  very  powerful  factor  in  the 
restriction  of  communicable  and  infectious  diseases  in  childhood. 

The  Dangers  from  Focal  Infection?..— For  years  the  dental  profession 
has  appreciated  the  toxic  influence  on  the  system  of  unsanitary  mouths 
and  the  dangers  presented  to  the  individual  by  such  mouths  incubating 
hundreds  of  millions  of  bacteria.  It  has  been  apparent  that  among 
adults  infections  of  the  system  were  taking  place  around  the  necks  of 
the  teeth,  through  the  inflamed  and  diseased  tissues  which  support  the 
teeth,  but  it  was  not  until  the  .r-ray  revealed  the  infected  areas  at  the 
ends  of  the  roots  that  dentistry  appreciated  to  the  utmost  the  serious- 
ness of  neglected  mouths  and  pulpless  teeth.  These  apical  infections 
are  difficult  for  the  layman  to  understand,  because  they  produce  no 
soreness,  no  pain,  no  inflammation,  no  pus.  They  are  caused  by  a  type 
of  bacteria  known  as  the  streptococcus  viridans,  which  is  quite  friendly 
and  harmless  in  the  mouth,  and  which  belongs  to  the  saprophytic  class. 
When  a  pulp  dies  in  a  tooth  these  bacteria  commonly  gain  ingress 
through  the  root  canal  of  a  tooth  to  the  apex,  or  out  into  that  area 
where  the  tissues  are  bathed  with  the  body  juices  or  serum.  In  this 
new  environment  they  gradually  change  their  nature  and  instead  of 
securing  their  food  from  dead  animal  or  vegetable  matter,  such  as  they 
found  in  the  mouth  around  the  teeth,  they  are  now  enabled  to  obtain 
their  nourishment  from  the  blood  serum  which  surrounds  them. 

Action  of  the  Bacterial  Toxin. — Like  all  bacteria,  they  exude  waste 
matter  from  their  bodies,  which  is  a  toxin;  but  these  bacteria,  being 
of  low  virulency,  do  not  create  as  vicious  a  toxin  as  many  of  the  patho- 
gens.   However,  the  toxin  is  of  sufficient  irritation  to  cause  the  osteo- 


316  APPENDIX 

ciasts  to  break  down  and  absorb  the  bony  wall  around  the  end  of  a  root 
of  a  tooth,  which  destruction  of  bone  may  be  readily  seen  in  the  .r-ray 
picture.  This  toxin  is  absorbed  by  the  lymphatic  vessels  and  its 
presence  in  the  blood  undoubtedly  excites  the  production  of  an  anti- 
toxin which  neutralizes  this  poison  and  may  successfully  control  it  for 
years.  As  long  as  the  individual  maintains  normal  health  and  the 
antitoxin  is  produced  in  sufficient  abundance  t6  act  as  a  neutralizer 
these  infected  areas  remain  harmless. 

Action  of  the  Bacteria. — ^The  longer  these  bacteria  live  in  this  environ- 
ment of  serum,  the  more  aggressive  they  become,  and  although  they 
do  not  seem  to  take  on  the  virulency  of  a  true  pathogen,  yet  when  the 
bodily  resistance  becomes  lowered  they  make  the  trip  from  the  end  of 
the  root  of  a  tooth,  through  the  lymphatics  and  into  the  blood  stream. 
These  microorganisms  vary  in  their  affinity  for  certain  tissues,  some 
finding  the  valves  or  the  lining  membrane  of  the  heart  the  most  favor- 
able, others  the  kidneys,  while  still  another  class  may  locate  in  the 
joints.  In  fact,  there  seems  to  be  no  limit  to  the  organs  or  tissues  in 
which  the  various  members  of  this  family  may  find  a  congenial  habitat. 
Having  once  located  in  a  favorable  environment  in  the  body,  they  again 
form  colonies,  and,  exuding  their  toxin,  so  poison  and  lower  the  activi- 
ties of  the  cells  of  the  tissues  upon  which  they  are  located  that  these 
cells  eventually  find  it  impossible  to  properly  functionate  and  carry  on 
their  individual  work,  and  we  have  the  beginning  of  a  diseased  tissue 
or  organ  of  the  body.  It  is  because  the  action  of  these  saprophytes  is 
so  slow  and  possesses  such  a  low  virulency  that  the  medical  and  dental 
professions  at  large  have  failed  to  grasp,  as  yet,  what  a  terrible  menace 
these  focal  infections  are  to  human  life,  and  again  the  sad  fact  is  that 
they  are  so  exceedingly  common^Jor  nearly  every  adult  has  one  or  more 
pulpless  teeth  in  his  mouth,  and  nearly  every  adult  will  show  under  the 
a;-ray  affected  areas  above  such  pulpless  teeth.  If  the  resistance  re- 
mains high  they  may  carry  such  infection  for  ten — ^yes,  twenty— years, 
but  a  colony  of  these  bacteria  living  within  bone  tissue  and  exuding 
their  toxin  into  the  blood  stream  will  sooner  or  later  create  systemic 
disturbance,  which,  if  not  taken  in  time,  will  mean  the  beginning  of  the 
end.  Recently  the  writer  has  been  demonstrating  for  his  own  satis- 
faction whether  the  streptococcus  viridans  found  in  these  infections 
had  developed  the  nature  of  a  pathogen.  In  a  number  of  cases  cultures 
made  from  infected  roots  proved  fatal  within  forty-eight  hours  after 
their  injection  into  mice. 

With  these  thoughts  in  mind,  it  must,  in  the  near  future,  be  recog- 
nized that  a  toothache  is  a  calamity,  for  most  toothache  means  that 
decay  has  already  reached  the  pulp,  and  a  dead  pulp  means  danger  of 
apical  infection.  The  best  root  filling  we  know  of  is  a  live  pulp. 
Therefore,  the  effort  must  be  made  to  prevent  decay  from  penetrating 
deep  enough  in  a  tooth  to  involve  a  pulp. 

When  these  various  pernicious  mouth  conditions  are  more  fully 
understood  as  the  one  greatest  factor  for  producing  disease,  medicine 


MOUTH  HYGIENE  IN  PUBLIC  SCHOOLS  317 

will  then  acknowledge  dentistry  as  its  greatest  specialty.  Also,  from 
a  prophylactic  standpoint,  wi'l  mouth  hygiene  be  considered  the  most 
important  branch  of  general  hygiene. 

Importance  of  a  Health  Program  in  Public  Schools. — It  must  soon  be 
apparent  to  educators  in  our  public  scho(jl  system  throughout  the 
country  that  a  health  program  of  considerable  magnitude  is  essential 
in  these  schools  for  the  prevention  and  correction  of  remediable  physical 
defects  among  the  children.  These  defects,  if  neglected,  may  e\'entu- 
ally  be  the  cause  of  the  child's  disability,  and  in  later  life  can  have  a 
detrimental  action,  morally,  mentally  and  physically.  Xo  longer  can 
they  specialize  on  mental  development  and  leave  the  body  of  the  child 
entirely  in  charge  of  home  influence.  The  findings  of  our  draft  boards 
have  conclusively  shown  us  the  fallacy  of  such  procedure.  If  we  study 
the  following  table  submitted  by  General  March,  of  the  U.  S.  Army, 
compiled  from  the  data  collected  by  the  draft  boards,  we  will  see  that 
there  has  been  dire  neglect  in  the  supervision  of  the  child's  body: 

"  The  effectives  at  ages  twenty-one  to  thirty,  for  approximately  ten 
million  men,  in  1917  were: 

Per  cent. 

21  years 46 

22  " 43 

23  " .' 39 

24  " 35 

25  "   .   . 32 

26  " 29 

27  " ^ 27 

28  " 26 

29  " , 23 

30  " 22 

The  effectives  at  the  ages  thirty-two  to  thirty-six  drop  to  less  than 
15  per  cent." 

Kention  is  called  to  the  rapid  accumulative  effect  of  physical 
er  the  adult  passes  thirty  years  of  age.  j 

has  stated  that  the  diseases  of  which  we  die  in  adult  life^^ 
ich  are  contracted  or  made  possible  in  early  youth. 
The  figures  in  General  March's  table  would  seem  to  corroborate  state- 
ments repeatedly  made  by  pathologists  that  after  thirty  years  of  age 
physical  resistance  to  disease  is  on  the  decline,  and  in  the  vast  majority 
of  people  can  only  be  maintained  in  middle  life  by  healthful  habits  and 
freedom  from  physical  defects  that  permit  bacterial  invasion  into  the 
system. 

This  demonstration  has  provided  sufficient  data  to  convince  us  that 
every  community,  sooner  or  later,  must  adopt  some  plan,  preferably  one 
of  prevention,  to  establish  clean  mouths  and  sound  teeth  for  school 
children. 

We  know  of  no  one  movement,  from  the  health  standpoint,  that 
would  be  more  beneficial  to  the  nation  at  large  than  a  serious  educa- 
tional campaign  to  eliminate  dental  caries,  as  far  as  would  be  possible. 
There  is  much  in  this  work  that  cannot  be  measured  in  figures,  especially 


318  APPENDIX 

the  moral  uplift  which  comes  to  the  individual  when  he  is  taught  the 
importance  of  cleanUness  and  a  wholesome  respect  for  his  body. 

The  prevention  of  diseases  such  as  syphilis,  tuberculosis,  dental 
caries,  etc.,  will  come,  not  through  any  specific  form  of  medication  or 
treatment,  but  chiefly  through  education  and  enlightenment.  Books, 
pamphlets,  articles  in  magazines  and  newspapers,  all  are  of  great  value 
in  disseminating  knowledge;  but  for  actual  tangible  results  in  eventually 
reaching  all  members  of  a  community,  nothing  will  compare  with 
thoroughly  spreading  such  knowledge  among  the  children  in  our  public 
school  system. 

The  results,  as  shown  in  this  report,  may  be  obtained  in  practically 
any  section  of  the  country,  if  the  hygienists  and  supervisors  in  charge  of 
the  work  are  sufficiently  educated  in  their  specialty.  It  must  be  clearly 
understood  that  although  the  dental  corps  has  been  guided  in  its  work, 
what  has  been  accomplished  has  been  mainly  through  its  own  intelligent 
individual  effort  and  not  through  any  coercion  of  the  teachers  by  the 
educational  authorities  in  charge  of  the  school  system.  This  demon- 
stration was  conducted  along  these  lines  under  the  least  favorable  cir- 
cumstances purposely  to  prove  the  real  efficacy  of  prevention.  It  is  our 
hope  that  from  now  on  a  definite  health  program  will  be  introduced  into 
our  school  system  in  Bridgeport  that  will  give  the  teachers  a  greater 
appreciation  of  the  importance  of  sound  bodies  for  the  children,  thus 
securing  a  complete  cooperation  and  interest  on  their  part  in  this  most 
important  phase  of  child  welfare.    ' 

SCHEDULE  OF  LESSONS  ON  MANIKINS. 

POLISHING  AND  INSTRUMENTATION. 

First. 

Teaching  the  four  motions — digital,  wrist,  rigid-arm  and  rotary. 

Grasp  of  pohshers. 

Direction  of  procedure  for  pohshing. 

First  three  divisions  of  polishing. 
Second. 

Fourth,  fifth,  sixth,  seventh  and  eighth  divisions. 
Third. 

Ninth,  tenth  and  eleventh  divisions  and  review  of  entire  labial  and  buccal  surfaces 
of  teeth  of  both  jaws. 
Fourth. 

Twelfth,  thirteenth,  fourteenth  and  fifteenth  divisions. 
Fifth. 

Sixteenth  and  seventeenth  divisions  and  review  of  entire  lingual  surfaces  of  teeth  of 
both  jaws. 
Sixth. 

Beginning  instrumentation. 

First  two  divisions. 
Seventh. 

Third,  fourth,  fifth,  sixth,  seventh,  eighth  and  ninth  divisions. 
Eighth. 

Practical  examination  on  polishing. 
Ninth. 

Theoretical-  (half-hour)  examination  on  polishing. 

Review  of  instrumentation — removal  of  varnish    and  plaster  from  teeth  of  lower 
jaw. 

Divisions  ten  and  eleven. 


SCHEDULE  OF  LESSONS  ON  MANIKINS  319 

Tenth. 

Twelfth,    thirteenth,    fourteenth,    fifteenth,    sixteenth,    seventeenth    and    eighteenth 
divisions  of  instrumentation. 
Eleventh. 

Review  instrumentation,  removal  of  varnish  and  plaster  from  teeth  of  upper  jaw. 

Divisions  nineteen  and  twenty. 

Use  of  floss  for  polishing  approximal  surfaces  and  use  of  brush  wheel  jor  occlusal 
surfaces. 
Twelfth. 

Examination.     Instrumentation    (practical)    and   instrumentation    (theoretical;. 

SYSTEM  FOR  INSTRUMENTATION. 

Division  1.     Fig.  166. 

Teeth.  Right  lower  molars,  bicuspds,  cuspid,  lateral  and    central. 

Surface.  Lingual. 

Instrument.  No.  18  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  between  left  lower  cuspid  and  bicuspid  on 

occlusal  surface. 
Motion.  Wrist  or  rotary. 

Division  2.     Figs.  167  and  168. 

Teeth.  Left  lower  central,  lateral,  cuspid,  bicuspids  and  molars. 

Surface.  Lingual. 

Instrument.  No.   17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  finger  on  cutting  edge  of  right  lower  cuspid  or 

lateral  for  left  lower  central,  lateral  and  cuspid. 
End  of  third  finger  on  cutting  edge  of  lower  centrals  for  bicuspids 

and  molars. 
Motion.  Rotary. 

Division  3.     Fig.  169.  *\ 

Teeth.  Left  lower  molars,  bicuspids  and  cuspid. 

Surface.  Buccal. 

Instrument.  No.   18  Darby-Perry. 

Fulcrum-point.     End  of  third  fingers  on  labial  surface  of  lower  incisors. 

Motion.  Wrist  or  rotary. 

Division  4-     Figs.  170  and  171. 

Teeth.  Lower  incisors,  right  lower  cuspid,  bicuspids  and  molars. 

Surface.  Labial  and  buccal. 

Instrument.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  or  third  finger  between  left  lower  cuspid  and 
bicuspid  for  lower  incisors. 
Advanced  on  incisors  for  cuspid,  bicuspids  and  molars. 
Motion.  Rotary. 

Divisions.     Figs.  172  and  173. 

Teeth.  Right  lower  molars,  bicuspids  and  cuspid. 

Surface.  Distal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  on  cutting  edge  of  lower  incisors  for  distal 

surface  of  last  molar. 
End  of  third  finger  on  labial  surface  of  right  cuspid  and  incisors 

for  the  balance. 
Motion.  Wrist  and  digital. 

Division  6.     Similar  to  Figs.  172  and  173. 

Teeth"  Left  lower  cuspids,  bicuspids  and  molars. 

Surface.  Dietal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  third  finger  on  labial  surface  of  lower  incisors 

Motion.  Wrist  and  digital. 


320  APPENDIX 

Division  7.     Similar  to  Fig.  174. 

Teeth  Right  lower  molars,  bicuspids  and  cuspid. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  third  finger  on  labial  surface  of  right  cuspid  and  incisors. 

Motion.  Wrist  and  digital. 

Division  8.     Fig.  174. 

Teeth.  Left  lower  cuspid,  bicuspids  and  molars. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Wrist  and  digital. 

Division  9.     Fig.  175. 

Teeth.  Lower  incisors. 

Surface.  Approximal. 

Instrument.  Nos.  5  and  6  Smith  set. 

Grasp.  Pen-holder. 
Fulcrum-point.     Third  finger  on  chin. 

Motion.  Wrist. 

Division  10.     Fig.  176. 

Teeth.  Right  upper  molars,  bicuspids,  cuspid,  lateral  and  central. 

Surface  Lingual. 

Instrumenl.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  third  finger  on  occlusal  surface  between  left  lower  cuspid 

and  bicuspid. 
Motion.  Wrist. 

Division  11.     Figs.  177  and  178.  yi. 

Teeth.  Left  upper  central,  lateral,  cuspid,  bicuspids  and  molars. 

Surface.  Lingual. 

Instrument.  No.  18  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  finger  on  cutting  edge  of  right  upper  cuspid. 

Motion.  Rotary. 

Division  12.     Fig.  179. 

Teeth.  Left  upper  molars,  bicuspids,  cuspid,  lateral  and  central. 

Surface.  Buccal  and  labial. 

Instrument.  No.  17  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  finger  on  labial  surface  of  left  upper  central  and 
lateral  and  end  of  third  finger  on  lingual  surface  of  right  upper 
central  and  lateral,  for  molars,  bicuspids  and  cuspid. 
End  of  third  finger  on  cutting  edge  of  right  upper  cuspid  for 
lateral  and  central. 

Motion.  Rotary. 

Division  IS.     Fig.  180. 

Teeth.  Right  upper  central,  lateral,  cuspid,  bicuspids  and  molars. 

Surface.  Labial  and  buccal. 

Instrument.  No.  18  Darby-Perry. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  and  fourth  finger  on  chin. 

Motion.  Rigid-arm  and  rotary. 

Division  14.     Fig.  181. 

Teeth.  Right  upper  molars,  bicuspids  and  cuspid. 

Surface.  Distal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  or  third  finger  on  labial  surface  of  lower  incisors,    j 

Motion.  Digital  and  wrist. 


SCHEDULE  OF  LESSONS  ON  MANIKINS  321 

Division  15.     Similar  to  Fig.  181. 

Teeth.  Left  upper  cuspid,  bicuspids  and  molars. 

Surface.  Distal. 

Instrument.  No.  13  Smith  set. 

Grasp.  Pen-holder.  " 

Fulcrum-point.  End  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 

Division  16.     Similar  to  Fig.  181. 

Teeth.  Right  upper  molars,  bicuspids  and  cuspid. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 

Division  17.     Similar  to  Fig.  181. 

Teeth.  Left  upper  cuspid,  bicuspids  and  molars. 

Surface.  Mesial. 

Instrument.  No.  14  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  or  third  finger  on  labial  surface  of  lower  incisors. 

Motion.  Digital  and  wrist. 

Division  18.     Similar  to  Fig.  175. 

Teeth.  Upper  incisors. 

Surface.  Approximal. 

Instrument.  Nos.  5  and  6  Smith  set. 

Grasp.  Pen-holder. 

Fulcrum-point.  Back  of  third  or  fourth  finger  on  chin. 

Motion.  Wrist  and  digital. 

Division  19.     Fig.  182. 

Teeth.  Lower. 

Surface.  Buccal,  labial  and  lingual. 

Instrument.  Sickle-shaped. 

Grasp.  Pen-holder. 

Fulcrum-point.  End  of  second  or  third  finger  on  cutting  edge  of  incisors. 

Motion.  Digital.     Draw  stroke. 

Division  20.     Fig.  183. 

Teeth.  Upper. 

Surface.  Buccal,  labial  and  lingual. 

Instrument.  Sickie-shaped. 

Grasp.  Pen-holder. 

'  Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin;   or   fist   grasp — end  of 

thumb  on  occlusal  surface. 
Motion.  Digital.     Draw  stroke. 

Division  21. 

Instrument.  Nos.   3  and  4  Harlan. 

Use.  For  small,  hard,  tenacious  deposits  under  gingival  border. 

Motion.  Draw  stroke. 

SYSTEM  FOR  POLISHING— LARGE  STICK. 


Division  1. 

Fig.  186 

Teeth. 

Upper  right  ce 

intral  and  lateral 

Surface. 

Labial. 

Grasp. 

Porte  polisher 

held  in  fist. 

Fulcrum-point. 

End  of  thumb 

on  cutting 

edge 

of  right 

cuspid. 

Motion. 

Digital, 

?1 

322  APPENDIX 

Division  2.     Fig.  187. 

Teeth.  Upper  right  cuspid,  first  and  second  bicuspids. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  third  finger  on  chin. 

Motion.  Rigid-arm. 

Division  3.,    Fig.  188. 

Teeth.  Upper  right  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary. 

Division  Jf..     Similar  to  Fig.  188. 

Teeth.  Lower  right  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Ftdcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary. 

Division  5.     Similar  to  Fig.  187. 

Teeth.  Lower  right  bicuspids  and  cuspid. 

Surface.  Buccal. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  second  finger  on  chin. 

Motion.  Rigid-arm. 

Division  6.     Fig.  189. 

Teeth.  Lower  incisors. 

Surface.  Labial.  w 

Grasp.  Fist. 

Fulcrum-point.     Thumb  or  first  finger  of  left  hand,  depressing  lips. 

Motion.  Rigid-arm. 

Division  7.     Similar  to  Fig.  187. 

Teeth.  Left  lower  cuspid  and  bicuspid. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  second  finger  on  chin. 

Motion.  Rigid-arm. 

Divisions.     Similar  to  Fig.  190. 

Teeth.  Lower  left  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rigid-arm. 

Division  9.     Fig.  190. 

Teeth.  Upper  left  molars. 

Surface.  Buccal. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rigid-arm. 

Division  10.     Similar  to  Fig.  187. 

Teeth.  Left  upper  bicuspids  and  cuspid. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     Back  of  third  finger  on  chin- 

Motion-  Rigid-arm, 


PROPOSED  MODEL  COURSE  323 

Division  11.     Similar  to  Fig.  186. 

Teeth.  Left  upper  lateral  and  central. 

Surface.  Labial. 

Grasp.  Fist. 

Fulcrum-point.     End  of  thumb  on  cutting  edge  of  right  central. 

Motion.  Digital. 

Division  12.     Fig.  191. 

Teeth.  Right  lower  molars  and  bicuspids. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary  (or  using  side  of  stick  with  rigid-arm  motion). 

Division  13.     Fig.  192. 

Teeth.  Right  lower  cuspids  and  incisors. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second  or  third  finger  from  cutting  edge  of   incisors  to 

first  bicuspid. 
Motion.  Rotary.  ^ — • 

Division  l^.     Fig.  193. 

Teeth.  Left  lower  cuspid,  bicuspids  and  molars. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.     End  of  second   finger  on  labial  surface   of  lower   incisors. 

Motion.  Both  rigid-arm  and  rotary. 

Division  15.     Fig.  194. 

Teeth.  Left  upper  molars  and  bicuspids. 

Surface.  Lingual. 

Grasp.  Pen-holder  , 

Fulcrum-point.     End  of  third  finger  c  a.  labial  surface  of  right  lower  lateral  or  cuspid. 
Motion.  Rigid-arm  (or  third  finger  on  masticating  surface  of  right  upper 

bicuspid,  rotary  motion). 

Division  16.     Fig.  195. 

Teeth.  Left  upper  cuspid  and  upper  incisors. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point!     End  of  second  or  third  finger  on  cutting  edge  of  right  upper  cuspid. 

Motion.  Rotary. 

Division  17.     Fig.  196. 

Teeth.  Right  upper  cuspid,  bicuspids  and  molars. 

Surface.  Lingual. 

Grasp.  Pen-holder. 

Fulcrum-point.     Back  of  third  or  fourth  finger  on  chin. 

Motion.  Rotary. 


PROPOSED  MODEL  COURSE  FOR  THE  EDUCATION  AND 
TRAINING  OF  THE  DENTAL  HYGIENIST. 

At  the  request  of  several  persons  who  are  interested  in  the  problem 
of  educating  and  training  the  dental  hygienist,  the  writer  has  outlined 
what  he  considers  to  be  a  model  course  for  this  purpose. 

The  curriculum  is  based  upon  the  original  conception  of  the  service 
for  which  the  dental  hygienist  was  created.  The  announcement  of  the 
first  course  in  September,  1913,  is  quoted  as  follows: 

"  In  the  last  few  years  there  has  been  a  great  demand  for  women 
as  hygienists  and  prophylactic  operators  in  dental  offices,  for  it  is  a 
well-known  fact  that  at  least  80  per  cent,  of  dental  diseases  can  be 
prevented  by  following  a  system  of  treatment  and  cleanliness. 

There  is  now  also  developing  a  demand  for  these  women  in  public 
institutions  such  as  schools,  hospitals  and  sanitariums.  The  scientists 
and  learned  professional  men  have  no  means  of  spreading  their  findings 
and  knowledge  for  the  prevention  of  disease  to  the  public  except  through 
pamphlets,  newspapers  and  magazine  articles.  Although  these  have 
done  good  service  they  are  not  so  efficient  as  teachers  of  hygiene  and 
dental  prophylactic  workers  would  be." 

There  is  a  noticeable  tendency  on  the  part  of  some  training  schools 
to  divert  the  dental  hygienist  from  her  true  field  of  service  by  devoting 
a  portion  of  the  course  to  training  in  chair  assistance  to  dentists  and  oral 
surgeons.  Although  tihfe  need  of  dentists  and  oral  surgeons  for  trained 
assistants  is  very  apparent,  it  must  be  definitely  understood  that  this 
assistant  should  not  be  the  dental  hygienist.  Her  field  of  service  is 
in  no  way  analogous  to  that  of  the  nurse  or  chair  assistant.  It  is  very 
desirable  that  she  should  be  competent  and  willing  to  cooperate  in 
any  way  to  maintain  the  routine  of  an  office  or  dispensary,  but  it  is  not 
desirable  that  her  efforts  should  be  continually  diverted  into  fields 
of  service  which  do  not  require  her  highly  specialized  training.  The 
dental  hygienist,  as  the  original  announcement  shows,  was  created  to 
be,  primarily,  an  educator  for  hygiene  and  secondarily,  a  dental  pro- 
phylactic operator. 

In  the  following  outline  the  daily  schedule  is  planned  so  that  the 
majority  of  the  lectures  occur  in  the  morning  periods  when  the  mind 
is  alert  and  the  student  is  most  receptive.  The  afternoon  work  for 
the  greater  part  of  the  course  is  completed  at  three  o'clock;,  and  at 
no  period  is  it  continued  after  four  o'clock.  It  is  essential  that' 
the  student  shall  have  at  least  two  hou;rs  of  daylight  for  outdoor 
exercise  and  recreation  before  devoting  the  evening  to  study  and 
review.  A  very  definite  plan  has  been  followed  of  having  the  practical 
training  advance  only  as  the  theory  can  be  assimilated.  The  courses 
in  Physics,  Elementary  and  Biologic  Chemistry,  Physiology,  and 
Dental  Histology  could  be  strengthened  by  the  addition  of  some 
practical  laboratory  work. 

The  lecture  periods  during  March  and  April  are  devoted  to  training 
the  true  teacher  of  hygiene.  The  month  of  May  can  be  utilized  for 
broadening  the  clinical  experience  of  the  student.  There  should  be  an 
opportunity  during  this  month  for  the  student  to  put  into  practice  the 
teaching  of  hygiene  in  conjunction  with  the  dental  prophylactic 
treatment.  Several  periods  have  been  reserved  throughout  the  course 
for  lectures  on  special  subjects  of  interest  to  the  class, 


DENTAL  HYGIENISTS'  DAILY  PROGRAM— COURSE  OF  STUDY. 
Last  Week  of  September.     (First  Semester.) 


Sept. 

Monday. 

Tuesday. 

Wednesday. 

Thursday. 

Friday. 

Saturday. 

9-10 

Anatomy 

and  General 

Histology 

Physiology 

Anatomy 

and  General 

Histology 

Physiology 

Anatomy 

and  General 

Histology 

PhyBiology 

10-11 

Special 

Anatomy 

(Head,  Teeth, 

Jaws) 

Special 

Anatomy 

(Head,  Teeth, 

Jawsj 

2-3 

Physics 

Physics   ■ 

Physics 

October. 


9-10 

Anatomy  and 
General 
Histology 

Physiology 

Anatomy  and 
General 
Histology 

Physiology 

Anatomy  and 

General 

Histology 

Physiology 

10-11 

Physics 

Special 

Anatomy 

(Head,  Teeth, 

Jaws) 

Tooth  Carving 

Special 

Anatomy 

(Head,  Teeth, 

Jaws) 

Tooth  Carving 

Special 

Anatomy 

(Head,  Teeth, 

Jaws) 

11- 
12.30 

Tooth  Carving 

Tooth  Carving 

Tooth  Carving 

Tooth  Carving 

2-3 

Dental 
Histology 

Bacteriology 

and 
Sterilization 

Dental 
Histology 

Bacteriology 

and 
Sterilization 

Dental 
Histology 

November. 

9-10 

Anatomy  and 
General 
Histology 

Physiology 

Manikin 
Demonstration 

Physiology 

Anatomy  and 

General 

Histology 

10-11 

Elementary 

Biologic 
Chemistry 

Manikin 
Practice 

Special 

Anatomy  (Head, 

Teeth,  Jaws) 

Elementary 

Biologic 
Chemistry 

Manikin 
Demonstration 

11- 
12.30 

Manikin 
Practice 

Manikin 
Practice 

Manikin 
Practice 

2-3 

Dental 
Histology 

Bacteriology 

and 
Sterilization 

Comparative 

Dental 

Anatomy 

Bacteriology 

and 
Sterilization 

Comparative 

Dental 

Anatomy 

December   to   Christmas  Holidays. 

9-10 

Anatomy  and 

General 

Histology 

Physiology 

Manikin 
Demonstration 

Physiology 

Anatomy  and 

General 

Histology 

10-11 

Deposits  and 
Accretions 
upon  Teeth 

Manikin 
Practice 

Deposits  and 
Accretions 
upon  Teeth 

Dento- 
Chemistry 

Manikin 
Demonstration 

11- 
12.30 

Manikin 
Practice 

Manikin 
Practice 

Manikin 
Practice 

2-3 

Inflammation 

Dental  Caries 

Dental  Caries 

January. 


9-12 

Practical  Work   Children. 

2-3 

Dental 
Prophylaxis 

Pyorrhea 
Alveolaris 

Special 

Pyorrhea 
Alveolaris 

Dental 
Prophylaxis 

3-4 

Malocclusion 

Malocclusion 

February.     (Second  Semester.) 

9-12 

Practical  Work,  Children 

2-3 

Dental 
Prophylaxis 

Alveolar 

Abscess  and 

Focal  Infection 

Alveolar 

Abscess  and 

Focal  Infection 

Dental 
Prophylaxis 

3-4 

Mouth  Mani- 
festations of 
Systemic 
Disease 

Communicable 
Diseases 

Odontalgia 

Dermatology 

March. 


Monday. 

Tuesday. 

Wednesday. 

Thursday. 

Friday. 

Saturday. 

9-12 

Practical  Work,  Adults 

2-3 

Nutrition  and 
Dietetics 

Radiography 

Nutrition  and 
Dietetics 

Radiography 

Nutrition  and 
Dietetics 

3-4 

General 
Hygiene 

General 
Hygiene 

General 
Hygiene 

Prenatal 

Hygiene  and 

Infant  Feeding 

April 

9-12 

Practical  Work,  Adults 

2-3 

Nutrition  and 
and  Dietetics 

Pedagogy 

Personal 
Hygiene 

Pedagogy 

Personal 
Hygiene 

3-4 

School  and 
Child  Hygiene 

Industrial 
Hygiene 

School  and 
Child  Hygiene 

Public  Health 
Organization  and 
Administration 

May 
The  entire  month  of  May  is  spent  on  Practical  Work. 

SUMMARY— FIRST  SEMESTER 


Sept. 
Hours. 


Oct. 
Hours. 


Nov. 
Hours. 


Dec. 
Hours. 


Jan. 
Hours. 


Total  hrs. 
1st  Sem. 


Anatomy  and  General  Histology     . 

Physiology 

Physics 

Elementary  Biologic  Chemistry 

Dento-Chemistry 

Special  Anatomy  of  Head,  Teeth,  Jaws 

Dental  Histology 

Bacteriology  and  Steriliza,tion   . 
Comparative  Dental  Anatomy 

Dental  Caries 

Deposits  and  Accretions  upon  Teeth    . 

Inflammation 

Dental  Prophylaxis 

Pyorrhea  Alveolaris 

Malocclusion 


Total 


12 
12 


11 


60 


48 


32 


30 

30 

7 

8 

3 

18 

16 

16 

8 

6 

6 

3 


6 
169 


Practical  Work 


Tooth 
Carving 


Manikin 
Practice 


Manikin 
Practice 


33 


Practical 

Work, 

Children 

54 


Total  163 


SUMMARY— SECOND  SEMESTER 


Feb. 
Hours. 


Mar. 
Hours. 


Apr. 
Hours. 


May 
Hours. 


Total  hours. 


Dental  Prophylaxis    .      .      .      .      .      .      ... 

Alveolar  Abscess  and  Focal  Infection  . 

Odontalgia 

Dermatology 

Mouth  Manifestations,  Systemic  Disease 

Communicable  Diseases 

Nutrition  and  Dietetics 

General  Hygiene 

Radiography '    .      .      . 

Personal  Hygiene 

Pedagogy 

Pub.  Health,  Organization,  Administration  . 

School  and  Child  Hygiene 

Industrial  Hygiene 

Prenatal  Hygiene  and  Infant  Feeding     . 

Total 


32 


4 
36 


Practical 

Work 
Adult  72 


Practical 
Work 

72 


Practical 
Work 

72 


Practical 
Work 
112 


4 
4 
4 
4 
16 
12 


Total  328 


INDEX. 


Abscess,  blind,  206 

Adenoids,  44 

Air  cells,  anatomy  of,  24 

ethmoidal,  26 

mastoid,  26 
Alimentary  tract  in  dental  prophylaxis 

Alveolar  process,  anatomyjof,  34,  47 

histology  of,  74 
Anterior  aspect  of  skull,  22 

fossa  of  skull,  18 

lacerated  foramen,  19 

naies,  23 

palatine  fossa,  22 
Antra  of  Highmore,  anatomy  of,  24 
Apical  foramen  of  teeth,  46 
Aqueous  humor,  28,  29 
Arch  of  teeth,  definition  of,  116 
Artery,  maxillary,  internal,  anatomy  of 
42  >  J      , 

Arthritis,  oral  infection  and,  222 
Articulation,  temporomaxillary,  36 
Auditory  canal,  external,  29 
meatus,  external,  29 


B 

Baboon,  teeth  of,  91 
Bacteremia,  216 

Bacteria,  propagation  of,  dental  prophy- 
laxis and,  230  t-    f  j 
Base  of  skull,  19 
Bicuspid  teeth,  occlusion  of,  99 
Bicuspids,  anatomy  of,  50 

individual  characteristics  of  52 
BUnd  abscess,  206 
Blood  corpuscles,  137 

normal,  constituents  of,  137 

plasma,  138 

platelets,  137 

supply  of  dental  tissues,  40 
Bloodvessels  of  peridental  membrane,  72 

of  pulp,  64 
Bone,  inflammation  of,  147 
etiology  of,  147 

repair  of,  147,  148 
Bones,  maxillary,  inferior,  anatomy  of,  34 
superior,  anatomy  of,  33 

palate,  anatomy  of,  34 


Bony  sinuses,  anatomy  of,  24 
Brushing  of  teeth  in  prophylaxis,  274 
Brush-wheel  in  pohshing  of  teeth,  272 
Buccal  surface  of  teeth,  definition  of  117 
Bull-frog,  teeth  of,  82 


Callus,  definition  of,  148 
Capsular  ligaments,  94 
Capsule  of  Tenon,  26 
Caries,  dental,  112,  173,  186 
Carnivorous  animals,  teeth  of,  85 
Catarrhal  inflammation   136 
Cell,  223 

life,  factors  for,  225 
Cells,  air,  anatomy  of,  24 
Cementoblasts  of  peridental  membrane, 

Cementum,  anatomy  of,  46 

canahcuH  of,  63 

cells  of,  63 

function  of,  64 

histology  of,  61 

lacunae  of,  63 

lamellae  of,  61 
Cheeks,  anatomy  of,  37 
Choanse,  23 

Chordi  tympani  nerve,  42 
Choroid,  28 
CiUary  body,  28 

muscle,  28 

processes,  28 
Circulation,  normal,  137 
Circumvallate  papilte,  39 
Coats  of  eye,  27,  28 
Cock's  crest,  18 
Condyle  of  jaw,  36 
Conjunctiva,  26 

Conjunctivitis,  oral  infection  and,  221 
Connective  tissue,  138 
Connective-tissue  cells  of  pulp,  64 
Coronal  suture,  17 
Coronoid  process,  36 
Corti,  organ  of,  32 
Cranial  nerves,  anatomy  of,  40  42 
Cranium,  anatomy  of,  17  ' 

Crista  galli,  18 
Crocodiles,  teeth  of,  82 
CrystalUne  lens,  anatomy  of,  29 
Curve  of  Spee,  100 

(327) 


328 


INDEX 


Cuspids,  anatomy  of,  49 

distinguishing  points  between  upper 
and  lower,  50 
Cysts,  211 


Deciduous   teeth,    premature   loss    of, 

malocclusion  and,  127 
Dental  caries,  112,  173 

areas  of  immunity  to,  112 

of  susceptibility  to,  112 
lactic  acid  in,  180 
malocclusion  and,  113 
prophylaxis  and,  233 
saliva  in,  182 
clinics,  educational  and  preventive, 
for  school  children,  302 
industrial,  dental  hygienist  in, 

301 
municipal,  dental  hygienist  in, 
301 
crypt,  formation  of,  76 
folhcle,  formation  of,  76 
foramen,  inferior,  36 
granuloma,  206 

hygienist,  broad  field  of  service  of, 
299 
in  hospitals,  301 
in  industrial  dental  clinics,  301 
in  municipal  dental  cUnics,  301 
in  private  practice,  299 
proposed     model     course     for 
education  and  training  of,  324 
in  public  schools,  first  at  work 

in,  307 
in  sanatoriums,  301 
infections,  chronic,  systemic  effects 
from,  218 
focus  of,  218 

systemic  effects  from,  215 
mechanism,  human,  92 
papilla,  formation  of,  75 
prophylaxis,  223 

alimentary  tract  in,  227 
bacterial  propagation  in,  230 
brushing  in,  274 

of  buccal  surfaces,  280 
instructions  for,  280 
of  labial  surfaces,  280 
of  Ungual  surfaces,  283 
of  masticating  surfaces,  286 
number  of  daily,  286 
in  children,  273 
decomposing     food   debris   in, 

228 
dental  caries  and,  233 
dentifrices  in,  287 
diet  in,  294 
examination  of  adult  mouth  in, 

235 
floss  silk  in,  288 
gums  in,  276 


Dental  prophylaxis,  home  care  of  mouth 
and,  274 
hygienist  in,  235 
instrumentation  in,  239,  249 

four  motions  in,  244 
instruments  in,  246 
keratin  in,  275 
lime-water  in,  291 
of  lower  jaw,  instrumentation 

in,  240,  249 
polishing  in,  261 

brush-wheel  in,  272 
floss  in,  272 
system  of,  263 
principles  of,  234 
in  private  practice,  system  of, 

30(0 
pyorrhea  alveolaris  and,  232 
surfaces  of  teeth  in,  238 
syphilis  and,  232 
systemic  infection  and,  232 
tissue  stimulation  in,  276 
tooth-brushes  and,  278 
treatment  in,  238 
tubercidosis  and,  232 
of  upper  jaw,  instrumentation 
in,  241,  255 
pulp,  inflammation  of,   differential 

diagnosis  of,  195 
ridge,  formation  of,  75 
tissues,  blood  supply  of,  40 
nerve  supply  of,  40 
Dentin,  anatomy  of,  46 
^      caries  of,  186 
fibrils  of,  61 
function  of,  61 . 
histology  of,  60 
matrix  of,  61 

secondary,  histology  of,  66 
tubules  of,  61 
Dentifrices  in  dpntal  prophylaxis,  287 
Denture,  human,  study  of,  95 
Diet  in  dental  prophylaxis,  294 
Diffuse  osteomyelitis,  211 
Digastric  muscle,  93 
Distal  surf  ace  of  teeth,  definition  of,  116 
Dogs,  teeth  of,  87 


E 

Ear,  anatomy  of,  29 

cochlea  of,  32 

drum  of,  30 

external,  29 

internal,  31 

labyrinth  of,  31 

middle,  29 

ossicles  of,  30 

fvi^nction  of,  31 

vestibule  of,  32 
Elephant,  teeth  of,  92 
Eminentia  articularis,  36 
Enamel,  anatomy  of,  46 


INDEX 


329 


Enamel,  functions  of,  GO 

histology  of,  58 

organ,  formation  of,  75 

rods,  histology  of,  5,8 
Endocarditis,  oral  infection  and,  222 
Endolymph,  31 
Endothelial  cells,  138 

leukocytes,  138 
Eosiaophiles,  138 
Ethmoidal  air  cells,  26 
Eustachian  tube,  anatomy  of,  31 
Evolution  of  tooth  forms,  80 
Exacferbations,  20,9 
Expression,  muscles  of,  37 
External  auditory  canal  29 

meatus,  29 
Extraction   of   permanent    teeth,    mal- 
occlusion and, 127 
Exudation,  definition  of,  14^ 
Exudative  in^ammation,  136 
Eye,  coats  of,  27 

fibrous,  27 
nervous,  28 
vascular,  27 
Eyeball,  interior  of,  anatomy  of,  28 
Eyes,  anatomy  of,  26 

refracting  media  of,  29 

yellow  spot  of,  28 


Face,  anatomy  of,  22 

Facial  nerve,  anatomy  of,  42 

Fauces,  anatomy  of,  44 

Fibrinous  exudation,   definition  of,    142 

Fibroblasts  of  peridental. membrane,  71 

Fibrous  Goats  of  eye,  27 

Fifth  cranial  nerve,  anatomy  of,  40 

Fishes,  teeth  of,  82 

Fissure,  sphenoidal,  19 

sphenomaxillary,  22 
Fistula,  definition  of,  144 
Floor  of  nose,  anatomy  of,  24 
Floss  silk  in  dental  priophylaxis,  288 
in  polishing  of  teeth,  272 
Fones's  plan  of  mouth  hygiene  proposed 

in  1914,  303 
Food  debris,  decomposition  of,   dental 
prophylaxis  and,  228 
mastication  of,  105 
Foramen,  lacterated,  anterior,  19 
middle,  19 
optic,  19 
ovale,  19 
rotundum,  19 
Fossa,  palatine,  anterior,  22 
posterior,  22 
of  skull,  anterior,  18 
middle,  19 
posterior,  19 
zygomatic,  22 
Fossa;,  glenoid,  22 
nasal,  22 


Fossae,  sublingual,  36 
Fovea  centralis,  28 
Freinum,  37 
Frontal  sinuses,  anatomy  of,  25 


G 


Gastritis,  oral  infection  and,  222 
Geniohyoid  muscle,.  93 
Glands,  lachrymal,  29 

parotid,  43 

salivary,  43 

sublingual,  36,  44 

submaxillary,  36,  44 

tear,  29 
Glenoid  fossse,  20 
Gnarled  enamel,  59 
Granular  layer  of  Tomes,  61 
Granuloma,  dental,  206 
Gums  in  dental  propjiylaxis,  276 

histology  of,  74 


Hard  palate,  anatomy  of,  37 
Head,  anatomy  of,  17 
Heahng  by  first  intention,  definition  of, 
145 
by  second  intention,  definition  of, 
146 
Highmore,  antra  of,  anatomy  of,  24 
Horse,  teeth  of,  92 
Hospitals,  dental  hygienist  in,  301 
Human  dental  mechanism,  92 

denture,  study  of,  95 
Hygienist,  dental,  service  of,  in  prophy- 
laxis, 235 


Incisors,  anatomy  of,  47 

individual  characteristics  of,  49 
Inclined  plane  of  teeth,  definition  of,  116 
Industrial    dental    cHnics,    dental    hy- 
gienist in,  301 
Inferior  dental  foramen,  36 

maxillary  bones,  anatomy  of,  34 
Inflammation,  136 

of  bone,  147 

etiology  of,  147 

causes  of,  138 

catarrhal,  136 

chronic,  definition  of,  144 

circulatory  disturbances  and,  140 

classification  of,  136 

,  definition  of,  136 

of  dental  pulp,  differential  diagnosis 
of,  195 

disturbance  of  function  in,  141 

exudative,  136 

heat  in,  141 


330 


INDEX 


Inflammation,  hyperemia  in,  141 

injury  in,  140 

interstitial,  136 

pain  in,  141 

parenchymatous,  136 

of  pteridental  membrane,  differential 
diagnosis  of,  195 

redness  in,  definition  of,  141 

suppurative,  136 

swelling  in,  141 

symptoms  of,  141 

ulcerative,  136 
Instrumentation  in  dental  prophylaxis", 

239,  249 
Internal  maxillary  artery,  anatomy  of,  42 
Interproximal  spaces,  113 
Interstitial  inflammation,  136 
Intracellular  substance  of  pialp,  66 
Iris,  28 
Iritis,  oral  infection  and,  222 


Jaw,  condyle  of,  36 

lower,  instrumentation  of,  in  dental 

prophylaxis,  240,  249 
upper,  instrumentation  of,  in  dental 
prophylaxis,  241,  255 
Jaws,  development  of,  78 

growth  of,  malocclusion  of  teeth  and, 
128 


Kerahn  in  dental  prophylaxis,  275 


Labial  surface  of  teeth,  definition  of,  117 
Labyrinth  of  ear,  31 
Lachrymal  apparatus,  29 

gland,  29 

sac,  29 
Lactic  acid  in  dental  caries,  180 
Lambdoid  suture,  17 
Lamina,  formation  of,  75 
Lateral  aspect  of  skull,  22 
Lemurs,  teeth  of,  92 
Lesion,  definition  of,  140 
Leukocytes,  endothehal,  138 

mondnuclear,  138 

polymorphonuclear,  137 
Ligaments,  capsular,  94 

sphenomandibular,  94 

stylomandibular,  94 
Lime-water  in  dental  prophylaxis,  291 
Lingual  surface  of  teeth,  definition  of, 
117 

tonsil,  40,  44 
Lips,  anatomy  of,  37 
Lower  teeth,  occlusion  of,  96 


Ludwig's  angina,  213 

Lymphatics  of  mouth,  anatomy  of,  43 

of  peridental  membrane,  72 

of  pulp,  65 
Lymphocytes,  138 


M 


Macula  lutea,  28 
Malar  process,  34 
Malocclusion  of  teeth,  112 

classification  of,  120 

Angle's,  121 
definition  of,  119 
etiology  of,  126 

extraction    of     permanent 

teeth  and,  127 
lack  of  use  and,  128,  132 
pernicious  habits  and,  127 
premature  loss  of  decidu- 
ous teeth  and,  127 
growth  of  jaws  in,  128 
individual,  119 
in  school  children,  310 
Mandible,  93 

anatomy  of,  34 
muscles  moving,  36 
Manikins,  schedule  of  lessons  on,  318 
Masseter  muscle,  93 
Mast  cells,  138 
Mastication  of  food,  105    . 
y      muscles  of,  37,  9,3 
Mastoid  air  cells,  26 

antrum,  anatomy  of,  31 
Maxillary  artery,  internal,  anatomy  of, 
42 
bones,  inferior,  anatomy  of,  34 

superior,  anatomy  of,  33 
sinuses,  anatomy  of,  24 
infection  of,  213 
Meckel's  ganglia,  32 
Mental  foramina,  35 
Mesial  surface  of  teeth,  definition  of,  116 
Middle  fossa  of  skuU,  19 

lacerated  foramen,  19 
Molar  teeth,  occlusion  of,  99 
Molars,  lower,  anatomy  of,  54 
upper,  anatomy  of,  52 

individual  characteristics  of,  54 
Monkey,  teeth  of,  88 
Mononuclear  leukocytes,  138 
Mouth,  adult,  examination   of,  in  pro- 
phylaxis, 235 
anatomy  of,  32 
home  care  of,  in  dental  prophylaxis, 

274 
hygiene,  communicable  diseases  and, 
313 
in  pubHc  schools  of  Bridgeport, 
Conn.,  report  of  five  years  of, 
302 
retardation   of  school  children 
and,  311 


INDEX 


331 


Mouth,  lymphatics  of,  anatomy  of,  43 

mucous  membrane  of,  anatomy  of, 
37 

roof  of,  anatomy  of,  24 
Mouth-brushing,  278 
Mucous  membrane  of  mouth,  anatomy 

of,  37 
Municipal  dental  clinics,  dental  hygienist 

in,  301 
Muscles,  digastric,  93 

of  expression,  37 

geniohyoid,  93 

masseter,  93 

of  mastication,  37,  93 

moving  mandible,  36 

mylohyoid,  93 

pterygoid,  93 

temporal,  93 
Mylohyoid  muscle,  93 

ridge,  36 
Myositis,  oral  infection  and,  222 


N 


Nares,  anterior,  23 

posterior,  23 
Nasal  cavity,  blood  supply  of,  24 
nerve  supply  of,  24 

duet,  29 

fossae,  anatomy  of,  23 

neives,  18 

process,  34 

septum,  23 
Nasmyth's  membrane,  59 
Necrosis  of  bone,  148 

definitioii  of,  140 
Nephritis,  oral  infection  and,  222 
Nerve  supply  of  dental  tissues,  40 

of  ears  and  teeth,   interconnec- 
tion of,  32 
Nerves,  cranial,  ana;tomy  of,  40,  42 

nasal,  18 

of  peridental  membrane,  72 

of  pulp,  65 
Nervous  coats  of  eye,  28 
Neuman,  sheaths  of,  60 
Neuralgia,  197 

causes  of,  1 98 

definition  of,  197 

naturife  of,  197 

quinti  major,  198 
minor,  198 

treatment  of,  201 

type  of,  197 

varieties  of,  198 
Neuritis,  oral  infection  and,  222 
Nose,  floor  of,  anatomy  of,  24 


Occlusion  of  teeth,  45,  97 

definition  of,  116,  117 


Odontalgia,  191 
causes  of,  194 
definition  of,  191 
local,  194 
obscure,  196 
referred,  196 
Odontoblasts,  64 
Olfactory  groove,  18 
Optic  disk,  28 

foramen,  19 
Oral  foci,  218 

distribution  of  infection  from, 

218 
proof    of    systemic    infection 

from,  218 
secondary  lesions  in,  219 
infections,  arthritis  and,  222 
conjunctivitis  and,  221 
endocarditis  and,  222 
gastritis  and,  222 
general    and    special    diseases 

originating  from,  221 
iritis  and,  222 
myositis  and,  222 
nephritis  and,  222 
neuritis  and,  222 
otitis  media  and,  221 
pharyngitis  and,  221 
pyemia  and,  222 
relation  of,  to  general  health, 

203 
septicemia  and,  222 
/  tonsillitis  and,  221 

toxemia  and,  222 
Orbits,  anatomy  of,  22 
Organ  of  Corti,  32 
Ossicles  of  ear,  30 

function  of,  31 
Osteoblasts  of  peridental  membrane,  71 
Osteomyehtis,  definition  of,  147 

diffuse,  211 
Ostitis,  210 

definition  of,  147 
Otic  gangha,  32 

Otitis  media,  oral  infection  and,  221 
Otoliths,  32 


Pain,  definition  of,  192 

varieties  of,  193 
Palate  bones,  anatojny  of,  34 

hard,  anatomy  of,  37 

process,  34 

soft,  anatomy  of,  37 
Palatine  fossa,  a,nterior,  22 

posterior,  22 
Papillae  of  tongue,  39 
Parenchymatous  inflammation,  136 
Parotid  glands,  43 
"Path  of  least  resistance,"  definition  of, 

143 
Periapical  infections,  204 
acute,  206 


332 


INDEX 


Periapical  infections,  tooth  apex  in,  208 
Peridental  membrane,  anatomy  of,  47 
bloodvessels  of,  72 
cells  of,  71 
cementoblasts  of,  71 
changes  in,  with  age,  73 
definition  of,  67 
epithelial  elements  of,  72 
fibers  of,  68 

arrangement  of,  68 
fibroblasts  of,  71 
fuliction  of,  72 
histology  of,  64,  67 
inflammation     of,     differential 

diagnosis  of,  195 
lymphatics  of,  72 
nerves  of,  72 
osteoblasts  of,  71 
white  fibrous  connective  tissue 
of,  68 
Perilymph,  31 

PQriodontitis,  acute  local,  195 
chrojiic  local,  195 
general,  196 
Periostitis,  definition  of,  147 
Permanent   teeth,    extraction    of,    mal- 
occlusion and,  127 
Phagocytosis,  definition  of,  141 
Pharyngeal  topsil,  44 
Pharyngitis,  oral  infection  and,  221 
Pointing,  definition  of,  143 
PoUshing  of  teeth  in  prophylaxis,  261 
brush-wheel  in,  272 
floss  in,  272 
system  of,  263 
Polymorphonuclear  leukocytes,  137 
Posterior  fossa  of  skull,  19 
nares,  23 
palatine  fossa,  22 
Protruding  teeth,  definition  of,  117 
Pterygoid  muscles,  93 
Pulp,  anatomy  of,  46 
laloodvessels  of,  64 
cavity,  anatomy  of,  46 
chamber,  anatomy  of,  46 
connective^tissue  cells  of,  64 
function  of ,  66 
histology  of,  64 
intercellular  substance  of,  64 
lymplmtics  of,  65 
nerves  of,  65 
odontoblasts  of,  64 
Pulpitis,  acute,  195 
Pupil  of  eye,  28 
Pyemia,  216 

oral  infection  and,  222 
Pyorrhea  alveolaris,  166 
definition  of,  166 
dental  piopihylaxis  and,  232 
etiology  of,  169 
history  of,  166 
pathology  of,  166 
prevention  of,  169 
treatment  of,  171 


Refracting  media  of  eye,  29 
Repair  of  bone,  147 

defiiiition  of,  145 
Retina,  28 

Retruding  teeth,  definition  of,  117 
Rodents,  teeth  of,  88 
Roof  of  mouth,  anatomy  of,  24 
Root  canals,  anatomy  of,  46 
Rhinoceros,  teeth  of,  92 


Sac,  lachrymal,  29 
Saccule,  32 
Sagittal  suture,  17 
Saliva,  constituents  of,  150 
decomposition  of,  154 
in  dental  caries,  182 
Salivary  glands,  anatomy  of,  43 
Sanatoriums,  dental  hygienist  in,  301 
Sapremia,  217 
Sella  turcica,  19 

Semicircular  canals,  anatomy  of,  32 
Sensation,  causes  of,  192 
definition  of,  192 
laws  governing,  192 
Septicemia,  definition  of,  143    ^ 

oral  infection  and,  222 
Septum,  nasal,  23 
Serous  exudation,  definition  of,  142 
Seventh  cranial  nerve,  anatomy  of,  42 
Sheaths  of  Newman,  61 
Sinus,  definition  of,  144 

sphenoidal,  anatomy  of,  25 
SinuseSj  frontal,  anatomy  of,  25 

maxillary,  anatomy  of,  24 
Skull,  anatomy  of,  17 

anterior  aspect  of,  22 
base  of,  19 
fossa  of,  anterior,  18 
middle,  19 
posterior,  19 
lateral  aspect  of,  22 
Snakes,  teeth  of,  82 
Soft  palate,  anatomy  of,  37 
Spee,  curve  of,  10,0 
Sphenoidal  fissure,  19 

sinus,  anatomy  of,  25 
Sphenomandibular  hgament,  94 
Sphenomaxillary  fissure,  22 
Stylomandibular  ligament,  94 
Subungual  fossse,  36 

glands,  36,  44 
Submaxillary  glands,  36,  44 
Superior  maxillary  bones,  anatomy  of,  33 
Suppurative  exudation,  definition  of,  142 

inflammation,  136 
Suspensory  ligament  of  lens,  29 
Sutures,  coronal,  17 
lambdoid,  17 
sagittal,  17 


INDEX 


333 


Sword  fish,  teeth  of,  92 
Symphysis  menti,  35 
SyphiUs,  dental  prophylaxis  and,  232  _ 
Systemic  infection,   dental  prophylaxis 
and,  232 


Tartar,  chemistry  of,  152 
color  of,  162 
definition  of,  149 
development  of,  157 
formation  of,  150 
hardness  of,  160 
removal  of,  160 
solubihty  of,  163 
Tear  gland,  29 
Teeth,  accretions  on,  149 
alveolar  process  of,  47 

histology  of,  74 
anatomy  of,  45,  47 
apical  foramen  of,  46 
arch  of,  definition  of,  1 16 
attachment  of,  66 
of  baboon,  91 
bicuspids,  anatomy  of,  50 

occlusion  of,  99 
buccal  surface  of,  definition  of,  117 
of  bullfrog,  82 
of  carnivorous  animals,  85 
cementing  substance  of,  58 
cementum  of,  anatomy  of,  46 

histology  of,  61 
of  crocodiles,  82 
cuspids,  anatomy  of,  49 
deciduous,  anatomy  of,  56 

premature  loss  of,  malocclusion 
and,  127 
dentin  of,  anatomy  of,  46 

histology  of,  60 

secondary,  histology  of,  66 
deposits  on,  149 

distal  surface  of,  definition  of,  116 
of  dogs,  87 
of  elephant,  92 
enamel  of,  anatomy  of,  46 

histology  of,  58 
eruption  of,  approximate  age  for,  57 
of  fishes,  82 
formation  of,  75 
forms  of,  evolution  of,  80 
functions  of,  secondary,  91 

supplementary,  109 
of  horse,  92 
histology  of,  58 
incisors,  anatomy  of,  47 
inclined  plane  of,  definition  of,  116 
infected,  source  of  systemic  disease, 

213 
labial  surface  ofj  definition  of,  117 
of  lemurs,  92 

lingual  surface  of,  definition  of,  117 
lower,  occlusion  of,  96 


Teeth,  malocclusion  of,  112 
classification  of,  120 

Angle's,  121 
definition  of,  119 
etiology  of,  126 

extraction    of    permanent 

teeth,  127 
lack  of  use  and,  128,  132 
pernicious  habits  and,  127 
premature  loss  of  decidu- 
ous teeth  and,  127 
growth  of  jaws  in,  128 
individual,  119 
in  school  children,  310 
as  a  masticating  machine,  80 
mesial  surface  of,  definition  of,  116 
model  of,  definition  of,  117 
molars,  lower,  anatomy  of,  54 
occlusion  of,  99 
upper,  anatomy  of,  52 
of  monkey,  88 
nomenclature  of,  47 
normal  contacts  in,  115 
occlusion  of,  45,  99 

definition  of,  116,  117 
peridental  membrane  of,    anatomy 
of,  47 
histology  of,  64,  67 
permanent,     extraction     of,     mal- 
occlusion and,  127 
protruding,  definition  of,  117 
pulp  of,  anatomy  of,  46 
cavity,  anatomy  of,  46 
chamber,  anatomy  of,  46 
histology  of,  64 
retruding,  definition  of,  117 
of  rhinoceros,  92 
of  rodents,  88 

root  canal  of,  anatomy  of,  46 
of  snakes,  82 
surfaces  of,  in  dental  prophylaxis, 

238 
of  sword  fish,  92 
of  turtles,  82 
upper,  occlusion  of,  96 
of  walrus,  92 
Temporal  muscle,  93 
Temporomaxillary  articulation,  36 
Tenon,  capsiile  of,  26 
Tic  douloureux,  198 
Tissue  stimulation  in  dental  prophylaxis, 

276 
Tomes,  granular  layer  of,  61 
Tongue,  anatomy  of,  38 

papillae  of,  39 
Tonsil,  lingual,  40 
Tonsillitis,  oral  infection  and,  221 
Tonsils,  anatomy  of,  44 
Tooth  germ,  formation  of,  75 
Tooth-brushes,  dental  prophylaxis  and, 

278  _ 
Toxemia,  216 

oral  infection  and,  222 
Trifacial  nerve,  anatomy  of,  40 


334 


INDEX 


Tuberculosis,    dental    prophylaxis    and, 

232 
Turkish  saddle,  19 
Turtles,  teeth  of,  82 
Tympanic  membrane,  30 


U 


Ulcer,  definition  of,  144 
Ulcerative  inflammationi  136 
Upper  teeth,  occlusion  of,  96 
Utricle,  32 


Vascular  coats  of  eye,  27 
Vitreous  humor,  29 


W 

Walrus,  teeth  of,  92 
Wharton's  duct,  36 


Zygomatic  fossa,  22 


RK53 
Fones 

l2^  hygiene. 


P73 
1921 


^/, 


> 


)yi^ 


JAN  2  1-1949 


-^ 


^^^ 


l^ 


